Possible #355. Watermark?

I have a possible #355. The edges lined up and perfs seem real. My only concerns are that the top edge looks slightly rough, the size is less than ideal (measures 24.5mm).

My big question though, is the watermark. It looks like a single-line, making it a fake from #378. Could it be the "skinny arm" of an upside down "U" from a double-line mark, though?

I think that it is probably genuine. The straight edges are parallel but you need a 1200dpi scan or higher to know for sure. The bit of roughness is normal. Clark/cfrphoto calls them "Hesitation Marks". The bottom one could be "too" straight. The perforations look decent on an Srail test and appear genuine. The watermark could be a Double Line and we're just seeing the single line portion of the "U". The triangle at top would rest off of the stamp. That's the limit of my knowledge.

Do both straight edges feel the same?

Clark/cfrphoto has a nice image and discusses them here: https://goscf.com/t/43654#374403

Thanks, Historical. I'll check the edges when I get home.

The edges do feel the same. I know 25mm (and 21.5mm for horizontal coils) is ideal, but is there a minimum size for these coils?

The reply after Clark's on the thread that I linked to does allude to the 5c perf 12 coil being "...never near the ideal of 25mm." I believe that I have read the same thing here on SCF, but cannot find it after a moderately exhaustive search.

The CV of #355 is debatably high enough to warrant certification. Considering how difficult it is to identify genuine perf 12 coils, it seems to me worthwhile of the cost to know for sure.

Do scan your stamp at 1200 or higher dpi and compare how parallel the straight edges are. Both of them "feeling" the same is a positive indicator of genuineness in my opinion given that the top edge appears genuine.

EDIT: Found it finally. Clark/cfrphoto at https://goscf.com/t/43601#373809 :



Clark or anybody who knows, how short is too short for the 5c flat plate coils?

The "cut" doesn't look right on the edges (regardless of height or "parallel-ness".) Likely a trimmed Scott 334 IMO.

Ken, is the top too rough to be hesitation marks and the bottom edge too clean?

my guess: no good

Just doesn't look right - hard to describe, but immediately evident if you've looked at thousands of genuine flat plate coils. My guess is that anything resembling a "hesitation" mark is actually either evidence of perf holes that weren't quite trimmed away, or just some roughness from whatever was used to trim the perfs off (e.g. dull box cutter, cheap scissors, worn ruler, etc.) True "hesitation" marks would line up exactly top to bottom (like puzzle pieces fitting together,) and I see no evidence of that.

Ah, I didn't know that about hesitation marks. Thanks.

Bottom edge is worrisome to me. Looks pretty sharp.

"Likely a trimmed Scott 334 IMO." Sorry about the typo - of course I'm sure most everyone figured out that I meant 335 (5c), not 334 (4c)...