Marked check. Many concerns have a private mark which they put on their checks. This mark is
known to the banks where the concerns keep their accounts and its absence from a check is
sufficient reason for withholding payment until the concern by which it purports to have been
drawn can be communicated with to find out whether the check is genuine. The purpose of the
mark is to afford protection against forgery.  There is one disadvantage in placing a private mark
on a check. If a forger finds out this mark and places it on a forged check the check is more likely
to be paid by the bank than if the mark were not used.