Washington Franklin Mysteries - Need Some Ideas

I was going through an old family member stamp album to look at the W&F's that I hadn't taken the time to look at and came across these.
I have tried and tried but can find absolutely no sign of a watermark on any of them. All are 'PRR Co' perfins - not sure what that stands for but that's not the reason for my post. All are perf 12. All but the yellow 10c are clearly flat plate (no set-off). Problems:

1.There are no 8c or 10c Washingtons without watermark.
2. All perf 12 4c Washingtons have a watermark.
3. There are no A138 style Franklins without watermark.

(there is a thin on the bottom right 4c)




Reverse:


Reverse in a watermark fluid bath:


Any thoughts.

PS: I have no experience with the blue paper varieties so I'm not thinking about that.

How many times have you watermarked them? I often have to watermark them multiple times looking for the flash...and even then on some stamps I am never 100% sure.
Don

Rest assured that they are watermarked. These can be tough stamps to see the watermark but one thing that is a must is when "dipping" them use a black tray.

I had tried about a half-dozen times, always with a black plastic tray. Also tried scanning them wet for purpose of this post. Used natural light and incandescent light. Puff...puff...
I use magnification when I do it also.

I thought it could be hidden in the perfin, but no.

That's why I posted this. I'm at a loss.

Also used Retroreveal with both the wet and dry scans.

HI Caper 123,
I know the perfins are not the object of this post but for everyone's edification they are "Pennsylvania Railroad Co."

Rich

Thanks Rich, it was my guess.

I know there must be a watermark and have found the difficult ones are almost always the Single Line variety or the ones that hang around on the very edges of the stamp. These stamps defy detection tho and I will likely have to just assume they are S/L. It just rubs me wrong to assume something tho. Just interesting they are all the same perfin, all found at t he same time, and all defy detection.

Have you seen anything at all when it flashes?
Don

Don - I study them in different light, with and without magnification from the time they are first treated to dryness. Zippo. Not even a hint of watermark on most. The 10c had given me an odd looking possibility right in the midst of the perfin holes with a large, ghostly see thru type S, not the normal darker shade watermark.

You might look into the time frame that the perfin was being used once you are sure of the company/business using it. Perhaps there is a reference source with those collecting perfins? If you can narrow the time it may help, if there is no over-lapping use of the perfin between the 1908/09-1910/11 issues (this may be a stretch). Also, double line watermarks being a bit larger, usually (but not always) do have enough to be seen. If you absolutely can not find one, you could just default to a single line issue in absence of any trace that can be determined to be double line.