1 Cent Benjamin Franklin Design A155 - I'm Confused

Hi guys please see image as I am a little confused.I have 11 perforations across the top and 12 down the side which doesn't seem to exist on the identifier I have?

Plus the double stamp is a lighter green than the single stamp my measurements seem to be 19mm across 22 1/4mm, that is from green line to green line not the perforations if I understood correctly.....I am a novice at this and teaching myself as I go. I understand also that a 1/4 of a inch makes all the difference with this so is there a better way of checking than with two rulers?

Also the keen eyed of you will notice it has a December 1924 watermark and as far as I can see on my identifier that can only be #604 #594 or #596 but it can't be #604 as there are no 10 perforations leaving #594/596 but I refuse to believe I could be this lucky, so please someone tell me my cynicism is in fact correct.....

Any help i.e. where am I going wrong with the perforations? Is the lighter green just down to age rather than print.
Thanks in advance

Hi Chirripo & welcome to the forum!!

Perforations: you don't 'count' them - you measure them. With a perforation gauge. The measurements you're reading in a catalog tell you how many perforations exist within 2cm.

(Search 'perforation gauge' on this forum & you'll find lots of info...)

The 'Dec 24': is not a watermark - it is a cancellation. Also most likely it is December 24th - not December 1924. (The year appears to be on the bottom?)

Watermarks are embedded in the paper, and can usually only be seen by putting lighter fluid on the stamp. (Search 'watermarks' if interested...)

Chances are the first one is #552 & the pair are #632. But accurate perf measurements are needed to correctly ID them.

And sorry, but your refusal to believe you've found a 594/596 is very good thinking!

(Lots of info if you search '594' and / or '596')

I'd doubt the single is a 552... even at the distance from the pair, the
vertical perfs would appear to match the pair, without having to use a
photo editor to manipulate it.

Clarification. Perforations are not measured, they are gauged. A perforation gauge calculates the number of perforations in the space of 2 centimeters.
Don

Without gauging the vertical perforations the highest likelihood is that
the stamps are all #632 ~ 11.0 x 10.5 and (not) either 594, or 596.

Taking frame measurements is premature, without first knowing the gauge
of the vertical perforations.