Saturday news. (Watertown, S.D.) 19??-19??, 1917-03-01
Detecting Counterfeit
Currency BY a Device

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Science has come to Uncle Sans
aid in detecting and preventing coun-
terfeiting with a device recently in
vented by Capt. Thomas Z Porter,
head of the Chicago Office Of the
United States secret service. His
machine is especially intended to de-
.tect counterfeit bills or coins at the
moment the p%ossessor attempts to
pass them at a bank. Through the
aid of modern processes of printing
and engraving it is said that counter
Efeits can be made SO much like the
originals that they defy ordinary in
Espection, making a special machine
necessary for their detection.
Capt. Porter's contrivance depends
on the principle that a counterfeiter
rarely succeeds in making perfect,
original plates for his bills. Some
how or other there is always a slight
distortion in some part. To the cas-
uai eye the products of the counter
feiter look exactly like those Of Uncle
Sam. But most plate-engraying pro-
~cesses make use of photography at
one stage or another. The images OF
the bills must pass through a lens,
which passage is sure to distort them.
Though the distortion is slight, minute
comparison with a good bill reveals
the defects. The new machine is de-
signed to make the work of compar
ison easy.
The detector consists simply OF a
thick wooden frame about ten inches
or a foot square. On the top surface,
brass edgings are provided which
hold in place a large plate of glass
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one-fourth of an inch apart. Several
glass plates are provided, each with
a different set of rulings suited to the
fineness of the bill undergoing test.
Beneath the glass plate r two thin
oblong metal plates faced on their
upper surfaces with blotting paper
face to which a bill will readily adj
here. These metal plates rest side
by side beneath the glass and are
provided with handles at each end
extending beyond the glass. By means
of the handles the bills may be. shifted
around under the glass at will.
In using the machine a good bill
is placed on enc of the oblong metal,
plates, and the supposed counterfeit
oQ the other-each adhering to the
plotting paper upper surface Of its
respective plate. The ruled glass is
then placed down over the metal
plates and their accompanying bills,
and held in place by the brass edg-
ings at the side of the continuance.
The vertical lines on the glass are
numbered serially from left to right.
The horizontal lines are divided into
two sets, each designated by similar
groups of letters. The userof the
device merely slides the metal plates
around (using the handles projecting
beyond the glass at each end) until,
say, the upper left-hand orn of the
good bill rests beneath a certain
point of the Icross-hatching on the
glass, and the remainder of the bill
is correspondingly lined up and
square with the rest of the ross
Matching. Similarly the operator
brings the upper left-hand orner of
the bad bill to rest beneath the
proper point of the lower section of
the ruling-afterward likewise bring
ing the other parts of the bill into.
agreement with theI rest of the
squares.
All this, according to a contributor
to Popular Science Monthly, has the
effect of placing a good bill and a bad
bill squarely before an observer and
because of the cross-hatching OF the.
glass, of dividing up the surface of
each bill into similar squares, each
of which may be compared in detail.
AS is readily evident, il the bad bill
is distorted in any particular, the de-
feet VIII Immediately become appar-
ent under such close scrutiny as this
sectionalizing into small squares
makes possible.