As a first proposition to such a man, however, the expert in
chirography may put him to the proof that out of a dozen signatures of
his own name no two will be alike in general form. Then he may turn to
the authentic and forged signatures in almost any case and show to the
layman that the first question of forgery arose from the fact that
these two signatures at a first glance are identically alike to almost
the minutest detail. With all the skill which the forger has put into
his crooked work, he keeps to the old principle of copying the
authentic signature which he has in hand, and the more nearly he can
reproduce this signature in every proportion the more readily the
forgery can be proved.

One of the most important facts from which the expert may begin his
investigations of possible forgery is that every man using a pen in
writing has his "pen scope." This technical term describes the average
stretch of paper which a man may cover without lifting the pen from
the paper and shifting his hand to continue the line. In even the
freest, swinging movements of a pen where the hand follows the pen
fingers, there are occasional breaks in the lettering or undue stretch
of space between the words which will indicate a characteristic scope
of the pen if the specimens under investigation cover an ordinary
paragraph in length.

As applied to the signatures of the ordinary individual, this pen
scope will appear in some form in the signature. The writer may lift
his pen before he has spelled out a long Christian or surname, he may
indicate it in the placing of a middle initial or in the space which
lies between the initial and the last name. In the case of the
signature of one's name, too, it should be one of the easiest and
lest-studied group of words which he is called on to put upon paper.