1 cent Franklin from the Washington - Franklin series

[tomd]

I have a 1 cent Franklin that could be Scott # 331 or 374.

The only difference that I can see is the USPS watermark, 331 double line and the 374 single line.

Well what if you see no lines???

Is there another item that I could tell the differance between the two.

[Butterfly]

I don't know of any other difference other than the date of use (is it canceled with a date?).
I would presume it to be one of the single line watermark stamps then, as there are several positions in the pane where the single line watermark barely ticks the edge or corner of the stamp.
Here is what a full pane might look like:
 

[tomd]

First no date only wavy lines.

Second it is a top stamp due to a flat edge.





Which could be 374 Single Line Watermark

[tomd]

This would make it top one

fifth from the left

[khj]

Butterfly has a key point -- the watermark fragment hidden in the corner or along the edge can basically only happen for the single-line watermark. (NOTE: take care to check for double-line serifs.) Therefore, your stamp is almost certainly the single-line watermark if you can't make out any watermark at all. The intersections between the double-line watermarks are not big enough, so you are basically certain to see some "double-line" fragment somewhere.

But just to clarify, the watermark mat shown is only a sample placement. There is no attempt to align the stamp to the watermark. Therefore, one cannot plate the stamp position by its watermark for these stamps. The guideline at top tells us it is that the stamp is one of #2-#9 of the first row from either the Lower Left or Lower Right panes.