Also, as with baseballs, personalized autographs will lower the overall value. Other major factors include rarity of the photo, historical importance, picture quality and overall eye appeal. Photos are usually used as display items so the eye appeal is very important. Documents - The keys to determining the value of an autographed document are overall condition and content. Many letters will have folds or bends in them because of the mailing process so, as long as there are no major flaws such as tears or staining that affect the content, the value won't be affected very much.
Content is another major factor.
As a general rule, the more sports related content, the higher the value. Another content-related factor revolves around the amount handwriting found in the document. With all other things being equal, if a letter is handwritten, it is usually worth more than a letter that is typed. Collectors seem to like the personal touch the handwritten pieces offer. This guide should be used for non-game equipment.