One Cent Washington Green, Help To Verify?

After looking at Stamp Smarter, we have narrowed our possibilities
for this strip to being 443, 452, or 490.

It is a perf 10 vertically. The measurements are 22 mm high by
19.5 mm wide.

We read that the 443 is from flat plate printing. The ink that is on the rear of the stamp is green, red, and bluish black. Not quite sure what that would indicate. We have not looked at whether there is a watermark or not.

RLM stamps,

Based on your measurements of 19.5 wide this makes it a Rotary Press stamp. Thus it cannot be 443 (Flat Plate 19M wide). The Key now is the watermark. If it is unwatermarked(#490) with Single Line Watermark (#452).

Hope this helps.
Hobsun

Thank you Hobson,

I just did my first watermark test. It does not have one.That would make it the # 490. Back to the drawing board. At least now the next time I need to do that test, I will know that it is not very difficult to do.

I used a product called Harco, Safety, Philatelic Watermark Fluid.
I would guess that it could be an old jar. Would this product ever expire? There is no expiration date on it.

HLM,

Yes unfortunately the 490 is the cheaper of the two possibilities so luck was not on your side. I do not believe the fluid would ever go bad or expire. I personally use Rosonol for watermark deterction as this seems to highlight them better for me but each person has their own preference. Some watermarks are harder to see but I would think in this case (color of stamp and lack of any cancel to deal with) that a watermark if present would be easy to spot and this being a strip of 4 would also help.

Hobsun