1908 Franklin 331 Or 374

This stamp is 12 x 12 but I cannot find a watermark. the site 1847usa.com states all these have watermarks. I use w/m fluid from Mystic called "clarity". Would some other fluid be better?

The other thing is, the same website states that a straight-edge can be found on any side. Also, this stamp is issued in sheets and booklets (obviously this is not a coil stamp). My question is, how can you tell the difference between a sheet stamp with a straight edge vs. a booklet stamp? Does the solid line of ink on the straight edge mean anything?

With your example it is impossible to determine if it was from sheet or booklet. The plate layout for the 331 and 374 sheets were the same with the exception of the imprints. The basic flat plate 400 subject (sheet) layout is shown below. You will notice the horizontal and vertical guidelines separating the 4 panes.



The booklets had a different layout. The 331 booklets were printed either from 180 subject of 360 subject plates. The 374 booklet were printed only from 360 subject plates.

Below is the 180 subject layout. The plate has vertical and horizontal guidelines. The vertical guideline is used for cutting but the horizontal guideline is perforated.



Below is the 360 subject layout. The plate has vertical and horizontal guideline with cutting on both.

Thanks, Russ. Great information.

Any idea on making the watermark more visible?