Abstract:
A security envelope that allows a mail handler or recipient to inspect its contents for potentially harmful granular/powder substances without ever opening the envelope is provided. The envelope comprises a front see-through window and a rear see-through window that are registered, such that an observer of the envelope can view through the envelope to examine its contents. A security background may, in place of, or in addition to, the rear window, be provided on the inside of the envelope, such that the observer can additionally verify that the envelope was sent from a trusted source. In this case, the security background will be registered with the front window. The security background may be composed of nano-structures that appear as a standard background when viewed with the naked eye, but reveal identifying elements when viewed under magnification. These nano-structures may additionally be distorted or diffused in the present of any granular/powder substance, thereby alerting the observer of a potentially harmful substance. Additional features, such as coating the inside of the windows with the particle-attracting substance, or printing the security background with a particle attracting ink, may also be provided to increase detection of any granular/powder substance within the envelope.

Description:
FIELD OF THE INVENTION  
         [0001]    The present inventions pertain to the field of security documents, and more particularly, to secure envelopes that facilitate the detection of dangerous foreign substances contained therein.  
         BACKGROUND  
         [0002]    The importance of making the mail safe from insidious persons who desire to wreak havoc on the recipients of such mail has very recently become a national security issue. Previously, mail recipients needed only to be concerned with packages that were large enough to conceal explosive devices. Because standard-sized envelopes are typically not large enough to contain such devices, a recipient of an envelope sent through the postal service need not have been concerned by the simple act of opening the envelope. In the wake of biological warfare waged upon the citizens of the United States by terrorists, and their use of the United States Postal Service (USPS) as a convenient and pervasive conduit for such warfare, it has become evident that even envelopes may contain a hidden danger. In particular, it is now conceivable, and most probable in the future, that dangerous biological agents, such as Anthrax, can be concealed in envelopes in a powder form, and spread to the unfortunate recipient of the envelope when opened.  
           [0003]    There thus is a need to provide an envelope that can easily be inspected for dangerous foreign substances contained therein without having to open the envelope, which may otherwise expose the handler of the envelope to the dangerous foreign substance.  
         SUMMARY OF THE INVENTION  
         [0004]    The present inventions are directed to envelopes that carry registered front and rear see-through windows and internal security backgrounds that allow a mail handler or recipient of a sealed envelope to inspect its contents for potentially harmful granular/powder substances without ever opening the envelope.  
           [0005]    In accordance with a first aspect of the present inventions, a security envelope comprises a first see-through window disposed on the front of the envelope, and a second see-through window disposed on the rear of the envelope, wherein the windows are registered with each other. The entireties of the windows need not be registered and need not be the same size. Rather, only enough of the windows that allows light to pass through the envelope is needed. In one non-limiting preferred embodiment, the windows are integral and are wrapped around an edge of the envelope to form the windows on the front and back of the envelope. In another non-limiting preferred embodiment, the windows can be formed of discrete pieces of material. In any event, the windows are preferably positioned adjacent an envelope edge, so that the document or documents enclosed within the envelope do not fully obstruct light passing through the windows. Optionally, a second set of windows is disposed on the envelope, such as, e.g., near the edge opposite to where the first set of windows is positioned. In this manner, at least one of the window sets will always be unobstructed by an enclosed envelope regardless of how the document is positioned in the envelope.  
           [0006]    The envelope may optionally comprise a particle attracting substance, such as, e.g., a tacky or electrostatic substance, disposed on the insides of either or both of the windows. In this manner, the granular/powder substance will be more apt to stick to the windows, thereby clouding them and alerting the observer of a potential risk within the envelope. The particle attracting substance can optionally be applied to selected portions of the windows, such that a latent message appears on the window when exposed to the granular/powder substance. In this manner, an additional security measure for alerting the observer of a potential risk is provided. The windows can either be clear or colored to enhance the visual appearance of the granular/powder substance.  
           [0007]    In accordance with a second aspect of the present inventions, a security envelope comprises a see-through window disposed on one side of the envelope, and a security background disposed on the inner surface of the other side of the envelope. The entireties of the window and background need not be registered and need not be the same size. Rather, only enough of the window and background that allows the background to be inspected through the window is required. The window and background are preferably positioned adjacent an envelope edge, so that documents enclosed within the envelope do not fully obstruct the background. Optionally, another window/background set can be disposed on the envelope, such as, e.g., near the edge opposite to where the first window/background set is positioned. In this manner, at least one of the backgrounds will always be unobstructed by an enclosed envelope. Even more optionally, a second window can be disposed on the other side of the envelope and registered with the first window, such that light is transmitted through the envelope. In this case, the security background may be adjacent the second window, such that both the security background and the second window can be viewed through the first window. The first and second windows may be discrete or integral, as previously described.  
           [0008]    As previously described, a particle attracting substance can optionally be disposed on the inner surface of the window with similar substance alerting results. Even more optionally, the security background can be printed in a particle attracting ink, such as, e.g., a tacky or electrostatic substance. The security background is preferably of a composition that indicates to the observer that the envelope was sent from a trusted source. For example, the security background can be composed of a thermally-activated latent image that appears in the presence of heat.  
           [0009]    Alternatively, the security background can be composed of a plurality of nano-structures that appear as an integral pattern, but under magnification, appear as individual identifying elements. For example, the nano-structures can form an encrypted code, which when decrypted, reveals a predetermined and known message. Each of the nano-structures can be so small as to form a half-tone element, replacing the standard half-tone dots that are typically used in the printing process. In this case, each half-tone element can be derived from an image, such as a company logo, a picture, or message. Not only can the nano-structures indicate to the observer that the envelope was sent from a trusted source, the nano-structures can affirmatively alert the observer of the existence of a granular/powder substance, which will tend to obstruct or otherwise distort or diffuse the individual nano-structures under magnification. In this case, the nano-structures need not be formatted to indicate a trusted source of the envelope, although preferably the nano-structures have some uniqueness to them to provide additional security.  
           [0010]    In accordance with a third aspect of the present inventions, stationery comprises an envelope and a substrate (such as, e.g., a document) for placement within the envelope, a security background disposed on the document, and a see-through window disposed on one side of the envelope. Thus, rather than disposing the security background on the envelope itself, the security background is disposed on the document, such as, e.g., on the edge of the document. The envelope and document can be of a standard size, or alternatively, any size. The importance is that the sizes of the envelope and document, and the position of the window, are coordinated, such that when the document is inserted into the envelope, the security background on the document is registered with the window. The window and background can optionally have additional security features as previously described.  
           [0011]    In accordance with a fourth aspect of the present inventions, a security envelope comprises a see-through window that is disposed on one side of the envelope, and a particle attracting substance (such as, e.g., a tacky or electrostatic substance) disposed on at least a portion of the inner window surface. In one non-limiting embodiment, the particle attracting substance coats an entirety of the inner window surface, and in another non-limiting embodiment, the particle attracting substance coats selected portions of the inner window surface to achieve varying effects, such as, e.g., producing a latent image or message. Optionally, another see-through window can be provided on the other side of the envelope and registered with the first window to achieve the results previously described herein.  
           [0012]    In accordance with a fifth aspect of the present inventions, a particle attracting substance, such as, e.g., a tacky or electrostatic substance, can coat all or a portion of the inner surface of an envelope, such that any granular/powder substance sticks to the inside of the envelope, thereby preventing, or at least minimizing, the dispersal of the granular/powder substance into the air when the envelope is opened. In this manner, the risk that the mail handler or recipient will breathe the dangerous substance in upon opening the envelope is minimized. This feature can be used in combination with the other features disclosed herein, or alternatively as a stand-alone feature.  
           [0013]    Other and further aspects and features of the invention will become apparent from the following drawings and detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    In order to better appreciate how the above-recited and other advantages and objects of the present inventions are obtained, a more particular description of the present inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
         [0015]    [0015]FIG. 1 is a front view of a security envelope constructed in accordance with a preferred embodiment of the present inventions, wherein a single set of registered discrete front and rear windows are provided;  
         [0016]    [0016]FIG. 2 is a rear view of the security envelope of FIG. 1;  
         [0017]    [0017]FIG. 3 is a front view of the security envelope of FIG. 1, particularly illustrating a latent image produced in a front window;  
         [0018]    [0018]FIG. 4 is a front view of a security envelope constructed in accordance with another preferred embodiment of the present inventions, wherein a single set of registered integral front and rear windows are provided;  
         [0019]    [0019]FIG. 5 is a rear view of the security envelope of FIG. 4;  
         [0020]    [0020]FIG. 6 is a front view of a security envelope constructed in accordance with still another preferred embodiment of the present inventions, wherein a double set of registered discrete front and rear windows are provided;  
         [0021]    [0021]FIG. 7 is a rear view of the security envelope of FIG. 6;  
         [0022]    [0022]FIG. 8 is a front view of a security envelope constructed in accordance with still another preferred embodiment of the present inventions, wherein a registered window and security background are provided;  
         [0023]    [0023]FIG. 9 is a close-up of the security background of FIG. 8, wherein nano-structures are provided;  
         [0024]    [0024]FIG. 10 is a close-up of the security background of FIG. 8, wherein image-based nano-structures are provided;  
         [0025]    [0025]FIGS. 10 a - 10   d  are close-up views of different image-based nano-structures;  
         [0026]    [0026]FIG. 11 is a close-up of the security background of FIG. 8, wherein a latent thermochromic image or message is provided;  
         [0027]    [0027]FIG. 12 is a front view of a security envelope constructed in accordance with still another preferred embodiment of the present inventions, wherein a front window and a document with a security background are provided;  
         [0028]    [0028]FIG. 13 is a front view of a security envelope constructed in accordance with still another preferred embodiment of the present inventions, wherein a single set of registered discrete front and rear windows and security background are provided; and  
         [0029]    [0029]FIG. 14 is a rear view of the security envelope of FIG. 13. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    [0030]FIGS. 1 and 2 depict a sealed security envelope  100  that allows a mail handler or recipient of the envelope  100  to detect the presence of a granular/powder substance contained therein without opening the envelope  100 . In the illustrated embodiment, the envelope  100  is standard-sized (e.g., #10 envelope, which measures 4.12×9.5 inches and is the type usually used to carry 8.5×11 inch documents). It should be noted, however, that the envelope  100  can be any size that allows the principles taught by the present inventions to be implemented. As with typical envelopes, the envelope  100  comprises a front  102  (FIG. 1), a rear  104  (FIG. 2), and a pair of opposing edges  106  and  108 .  
         [0031]    The envelope  100  further comprises a set of see-through windows  110 , including a front window  112 ( 1 ) disposed on the front  102  of the envelope  100 , and a rear window  112 ( 2 ) disposed on the rear  104  of the envelope  100 . Each window  112  is composed of an optically transparent material, such as, e.g., plastic. The windows  112  are registered with each other, such that an observer of the envelope  100  can view the rear window  112 ( 2 ) when looking through the front window  112 ( 1 ), or alternatively view the front window  112 ( 1 ) when looking through the rear window  112 ( 2 ). In the illustrated embodiment, the entireties of the windows  112  are registered with each other, i.e., the perimeters of the windows  112  are aligned with each other. It is emphasized, however, that only a portion of the front window  112 ( 1 ) need be registered with a portion of the rear window  112 ( 2 ) without straying from the principles taught by this invention. In any event, the transmission of light through the envelope  100  via the window set  110  facilitates and enhances visual verification of any granular/powder substance otherwise concealed within the envelope  100 . It is anticipated that certain colors or combinations of clear and colors may enhance the visual identity, and thus detection, the granular/power substances.  
         [0032]    The window set  110  is positioned adjacent one of the edges  106  and  108  of the envelope  100 , and specifically the edge  108 , such that a substrate, e.g., a document  114 , does not totally block the passage of light through the window set  110 . For example, assuming the width of the envelope  100  to be 9.5 inches, an 8.5×11 inch document  114  enclosed within the envelope  100  will effectively leave 1 inch width of the envelope  100  unoccupied by the document  114 . Thus, the registered portions of the window set  110  should be positioned less than 1 inch from the edge  108  of the envelope  100 . In this manner, if the document  114  totally obstructs the window set  110  (e.g., if the edge of the document  114  abuts the edge  108  of the envelope  100 ), the observer need only tap the envelope  100  on the edge of the envelope  100  opposite the window set  110  (in this case, the edge  106 ) to force the document  114  to move away from the window set  110 , thereby allowing light to pass therethrough. It should be noted that although the window set  110  is depicted in the illustrated embodiment as being positioned adjacent the edge  108 , it can be suitably positioned anywhere on the envelope  100 , e.g., on its bottom edge.  
         [0033]    In the illustrated embodiment, the inner surfaces of the either or both of the windows  112  are coated with a particle attracting substance, such that any granular/powder substance adheres to the windows  112 . In this manner, the visual awareness of the granular/powder substance is enhanced and/or visual clarity of the window set  110  is subdued, thereby alerting the observer of the existence of a possibly dangerous agent within the envelope  100 . To prevent an insidious person from removing the particle attracting substance, the windows  112  are preferably treated with a substance that causes the windows  112  to change color in the presence of cleaning agents.  
         [0034]    The particle attracting substance can be, e.g., a tacky or electrostatic substance that attracts, or at the least holds the granular/powder substance when it makes contact with the window set  110 . In the case of a tacky substance, it is preferably not so tacky that it hinders the placement of documents within the envelope  100  (e.g., by automated machines), but tacky enough so that granular/powder substances within a reasonable particle size range adheres to the windows  112 .  
         [0035]    Optionally, the particle attracting substance can be applied to predetermined portions of the front window  112 ( 1 ) to form a latent warning image or message that appears when a granular/powder substance adheres to the particle attracting substance. For example, FIG. 3 illustrates exemplary latent message  116 , and particularly the message “Warning. Do not Opening,” which appears in the front window  112 ( 1 ) when it is exposed to a granular/powder substance.  
         [0036]    To maximize the amount of granular/powder substance exposed to the window set  110 , the observer, assuming that the document  114  is not totally obstructing the window set  110 , preferably taps the edge of the envelope  100  adjacent the window set  110  (in this case, the edge  108 , on a hard substance), while firmly grasping a portion of the envelope  100  adjacent the document  114  (such that the document  114  does not move towards and obstruct the window set  110 ). In this manner, any granular/powder substance contained within the envelope  100  will tend to move towards the window set  110 , thereby increasing the chances that the granular/powder substance will be detected.  
         [0037]    As illustrated in FIGS. 1 and 2, the windows  112  are discrete in that they are formed from separate pieces of material. Alternatively, as illustrated in FIGS. 4 and 5, a secure envelope  150  comprises a window set  160 , which includes integral front and rear windows  162 ( 1 ) and  162 ( 2 ) that are formed from a single piece of material. Thus, the front and rear windows  162 ( 1 ) and  162 ( 2 ) are formed by wrapping the material around an edge  158  of the envelope  150 . This provides a see-through envelope that is more easily or cheaply manufactured compared to the discrete window set  110  depicted in FIGS. 1 and 2.  
         [0038]    [0038]FIGS. 6 and 7 depicts another sealed security envelope  200 , which is similar to the previously described security envelope  100 , and to the extent that the features of the envelopes  100  and  200  are similar, identical reference numbers have been used. The envelope  200  differs from the envelope  100 , however, in that it carries two window sets  210  and  214  rather than a single window set. The first window set  210  includes front and rear windows  212 ( 1 ) and  212 ( 2 ), which are respectively disposed on the front and rear  202  and  204  of the envelope  200 . Likewise, the second window set  214  includes front and rear windows  216 ( 1 ) and  216 ( 2 ), which are respectively disposed on the front  202  and rear  204  of the envelope  200 . The provision of two window sets  210  and  214  allows visual inspection of the contents of the envelope  200  without having to adjust the position of a document  114  obstructing one of the window sets  210  and  214 . That is, if the document  114  completely obstructs the window set (in the illustrated embodiment, the window set  214 ), the other window set (in the illustrated embodiment, the window set  210 ) will not be obstructed by the document  114 . Thus, one of the window sets  210 ,  214  will always be unobstructed by the document  114 . In this case, as with the previously described window set  110 , the observer can tap the edge of the envelope  200  adjacent the unobstructed window set  210 , while firmly grasping a portion of the envelope  200  adjacent the document  114 . In this manner, any granular/powder substance contained within the envelope  200  will tend to move towards the unobstructed window set  210 , thereby increasing the chances that the granular/powder substance will be detected.  
         [0039]    [0039]FIG. 8 depicts another sealed security envelope  250  that allows a mail handler or recipient of the envelope  250  to detect the presence of a granular/powder substance contained therein without opening the envelope  250 . Like the previously described envelope  100 , the envelope  250  comprises a front  252 , a rear  254  with an inner surface  255 , and a pair of opposing edges  256  and  258 . Unlike the previously described envelope  100 , however, the envelope  250  includes a front see-through window  262  disposed on its front  102 , but does not include a rear see-through window. Instead, the envelope  250  comprises a security background  264  disposed on the inner rear inner surface  255  of the envelope  250 .  
         [0040]    The front window  262  is registered with the security background  264 , such that an observer of the envelope  250  can view the security background  264  when looking through the front window  262 . In the illustrated embodiment, the entireties of the front window  262  and the security background  264  are registered with each other, but it should be noted, that only portions of the front window  262  and security background  264  can be registered with each other without straying from the principles taught by this invention. Optionally, the envelope  250  can have a second window/background combination similar to the double window sets illustrated in FIGS. 6 and 7 such that the observer is provided a selection of windows to view.  
         [0041]    In the illustrated embodiment, the front window  262  is positioned, such that an edge  115  of a document  114  can be viewed. In this manner, the observer will be assured that it is the security background  264  on the envelope  250  that is presently being observed, rather than a bogus background printed on the document  114 . For example, assuming the width of the envelope  250  to be 9.5 inches and the width of the document  114  to be 8.5 inches, the left portion of the front window  262  will preferably be more than 1 inch from the edge  258  of the envelope  250  to ensure that, even if the document  114  abuts the edge  256 , the edge  115  of the document  114  will still appear in the front window  262 . The right portion of the front window  262 , however, should be positioned less than 1 inch from the edge  258  of the envelope  250  to ensure that the security background  264  is not totally obscured from view by the document  114 .  
         [0042]    In the illustrated embodiment, the security background  264  is unique to a known entity, such as a company. For example, the company can purchase security envelopes  250  that include customized security backgrounds  264  that identify it as the source that purchased the envelopes  250 . The company can then distribute the security envelopes  250  to its employees for use within the company or even outside the company when sending documents from the company to outsiders. The recipient of the envelope  250 , when he or she properly views the security background  264  through the front window  262 , will know that the company or at least one of its employees is the source of the envelope  250 , and will thus be assured that the envelope  250  does not contain a dangerous substance.  
         [0043]    As illustrated in FIG. 9, the security background  264 ( 1 ) comprises nano-structures  266 , which when viewed by the naked eye, appear as a half-tone background, but when magnified using, e.g., a magnifying loupe, appear as discrete items. In this case, the discrete items are a repeating series of alpha-numerical characters that form an encrypted code that, when decrypted, result in a predetermined and expected message. The recipient will then know that the envelope  250  was sent from a trusted source. As an additional measure, the nano-structures  266  are so small (e.g., less than 1 point in size), that their exposure to a granular/powder substance will typically obscure or diffuse the recognition of the individual nano-structures  266  when magnified. In this case, even nano-structures  266  that are not particularly unique, such as, e.g., (a non-unique pattern of polygons, circles or ovals, crosses or X&#39;s, or alpha-numerical characters) are useful in that they will alert the recipient that the envelope  250  may contain a dangerous substance if the security background  264 ( 1 ) has been exposed to a granular/powder substance.  
         [0044]    As a further measure, the ink used to print the security background  264 ( 1 ) can, itself, be composed of a particle attracting substance, such as, e.g., a tacky or electrostatic substance. In this manner, any granular/powder substance concealed within the envelope  250  will tend to stick to the security background  264 ( 1 ), thereby changing or diffusing its color in a manner that is detectable to the naked eye, in addition to obscuring the magnified individual nano-structures  266 . Further details on the use and design of nano-structures are disclosed in U.S. patent application Ser. No. 09/621,325, entitled “Security Document With Nano-Pattern,” which is fully and expressly incorporated herein by reference.  
         [0045]    [0045]FIG. 10 illustrates an alternative background  264 ( 2 ), which like the security background  264 ( 1 ) illustrated in FIG. 9, comprises nano-structures  268 . These nano-structures  268 , however, are derived from images, such as corporate logos, photographs, pictures, or key words or phrases, that are converted into half-tone dots, which replace conventional round dots typically used in normal commercial printing. For example, each nano-structure  268  illustrated in FIG. 10 can be derived from an image of an American Flag (FIG. 10 a ), George Washington (FIG. 10 b ), Liberty Bell (FIG. 10 c ), or a California bear (FIG. 10 d ). Like the nano-structures  264  described above, the nano-structures  268  allow the recipient to verify the source of the envelope  250 , and provide the additional security measure of becoming visually obscured in the presence of a granular/powder substance. The security background  264  can also be composed of a particle attracting ink with similar results. Further details on the use and design of image-derived nano-structures are disclosed in U.S. Provisional Patent Application Serial No. 60/312,170, entitled “Security Document Manufacturing Method Using Halftone Dots That Contain Microscopic Images,” which is fully and expressly incorporated herein by reference.  
         [0046]    [0046]FIG. 11 illustrates still another alternative background  264 ( 3 ), which employs thermochromic technology. The security background  264  comprises a latent image  270  (e.g., “Verify First”), which includes a foreground  272  printed in a thermochromic ink, and a background  274  printed in a non-thermochromic ink. Under normal thermal conditions (such as, e.g., at room temperature), the colors of the foreground  272  and background  274  are matched, such that the security background  264  appears uniform to the observer. When the security background  264 ( 3 ), however, is thermally activated (such as, e.g., by rubbing, or otherwise heating, the rear  254  of the envelope  250 ), the foreground  272  changes color, and the latent image  270  visually appears to the observer. Alternatively, the foreground  272  is composed of a non-thermochromic ink, and the background  274  is composed of a thermochromic ink to product the latent image  270 . Even more alternatively, both the foreground  272  and background  274  can be composed of thermochromic ink that are differently colored when thermally activated. Further details on the use and design of thermochromic latent images are disclosed in U.S. Pat. No. 5,636,874, entitled “Temperature Sensitive Security Document,” U.S. Pat. No. 5,873,604, entitled “Document Security System Having Thermo-Activated Pantograph and Validation Mark,” and U.S. patent application Ser. No. 09/046,571, entitled “Variable Density Verification,” all of which are fully and expressly incorporated herein by reference.  
         [0047]    [0047]FIG. 12 depicts still another sealed security envelope  300 , which allows a mail handler or recipient of the envelope  300  to detect the presence of a granular/powder substance contained therein without opening the envelope  300 . The envelope  300  is similar to the envelope  250  previously described with respect to FIG. 8, and to the extent that the features of both are similar, identical reference numbers have been used. The envelope  300  differs from the envelope  250 , however, in that the envelope  300  itself does not include a security background. Rather, a document  314  is provided with the security background  264 . In particular, the security background  264  is printed an edge  315  of the document  314 , such that when the document  314  is enclosed within the envelope  300 , the security background  264  will appear in the front window  262 .  
         [0048]    Like with the envelope  250  of FIG. 8, the front window  262  is positioned, such that the edge  115  of the document  114 , and thus, the security background  264 , can be viewed through the window  262  by an observer. Optionally, in addition to providing the security background  264  on the document  114 , the same security background  264 , or even a different security background, can be included on the inner rear surface of the envelope  300 , similar to the envelope  250  of FIG. 8. In any event, the security background  264  can include any or all of the features previously described with respect to the security background  264  of the FIG. 8 envelope  250  with similar results.  
         [0049]    [0049]FIGS. 13 and 14 depict still another sealed security envelope  350 , which allows a mail handler or recipient of the envelope  300  to detect the presence of a granular/powder substance contained therein without opening the envelope  350 . The envelope  350  combines the features of the envelopes  100  and  250  of FIGS. 1 and 8. To the extent that the features of both are similar, identical reference numbers have been used. Like the envelopes  100  and  250 , the envelope  350  comprises a front  352 , rear  354 , and opposing edges  356  and  358 .  
         [0050]    The envelope  359  further comprises a set of see-through windows  360 , including a front window  362 ( 1 ) disposed on the front  352  of the envelope  350 , and a rear window  362 ( 2 ) disposed on the rear  354  of the envelope  350 . Like with the window set  110  of the FIG. 1 envelope  100 , the windows  352  are registered with each other, such that an observer of the envelope  350  can view the rear window  362 ( 2 ) when looking through the front window  362 ( 1 ), or alternatively view the front window  362 ( 1 ) when looking through the rear window  362 ( 2 ). The windows  362  can be coated with a particle attracting substance similar to that applied to the windows  112  of the FIG. 1 envelope  100 .  
         [0051]    The envelope  350  further comprises a security background  364  disposed on the inner rear surface  355  of the envelope  350  similar to the FIG. 8 envelope  250 . The front window  362 ( 1 ) is registered with the security background  364 , such that an observer of the envelope  350  can view the security background  364  when looking through the front window  362 ( 1 ). As illustrated, the security background  364  is adjacent the rear window  362 ( 2 ), such that the size of the front window  362 ( 1 ) can be minimized and both the rear window  362 ( 2 ) and the security background  364  can be viewed through the front window  362 ( 1 ). It is noted that the size of the front window  362 ( 1 ) is larger than that of the rear window  362 ( 2 ) to enable this to happen. The security background  364  can include any or all of the features previously described with respect to the security background  264  of the FIG. 8 envelope  250  with similar results.  
         [0052]    Optionally, the envelope  350  can have a front window/back window/background combination similar to the double window sets illustrated in FIGS. 6 and 7, such that the observer is provided a selection of windows to view. Even more optionally, the security background  364  can, in addition to be being disposed in the inner rear surface  355 , is also disposed on the edge of the document  114  similar to the document  314  of FIG. 12.  
         [0053]    While embodiments and applications of this invention have been shown and described, it would be apparent, to the readers of this description, that many more modifications are possible without departing from the inventive concepts described herein. The invention, therefore, is not to be restricted beyond the scope and in the spirit of the appended claims.