Bank-notes are altered in two ways, namely: raising the denomination,
and changing the name of a broken to that of a responsible bank.
First, in altering a note, it is scraped until thin: then figures of
larger denomination are pasted over. A pasted note may be detected by
holding it up to the light, when the pasted parts will appear darker,
as they are thicker.
Second, the denomination of a note is raised by taking out a low one
with an acid, and printing in a higher one with a counterfeit stamp.
The ink used in genuine bank-note printing is a peculiar kind, and
not easily to be obtained by counterfeiters: therefore, their printing
will not appear as clear and bright as that of the government, which
is done with ink of the finest quality. If the ink is black, it gives
a clear and glossy impression, without any of that smutty appearance,
as is sometimes seen in counterfeit bank-notes. It is almost
impossible to imitate the green ink that is used by the government,
and it is nearly as difficult to imitate the red and other colors.
Counterfeit inks look dull and muddy, while genuine inks have a glossy
appearance.
In the case of a note altered by the use of acid, it may be
noticed that the acid, by spreading more than was intended by the
counterfeiter, has injured parts of other letters, and the paper will
appear more or less stained by the acid.