Watermark Check - There is no need to check the watermark on this stamp other than for authentication purposes. This stamp must be printed by the rotary press method on unwatermarked paper. Note that this is the only Franklin Head that was printed using the Rotary Press Method. Therefore, if the 10¢ Franklin is rotary, i.e. wider than the flat plate stamp, it must be genuine. It is unlikely that unused copies of this stamp would be faked by trimming a perf 10 stamp, since the coil is less expensive than the fully perforated stamp in the unused state. However, the used coil stamp may be faked by trimming the perf 10 stamp, since the used coil is valued about 10 times more than the used sheet stamp. Fortunately, this is an easy stamp to check, if it is rotary it is genuine, if it is flat plate it is fake.
The more common fakes of this stamp are the line pairs, since creating one from a normal coil pair simply involves drawing in a line. The line will not be engraved, however, and will not create an impression on thin foil (see the "thin foil" method.