? Scott 366 . A Novice, Could This Be Treasure?

I'm new to this, but I've done my studying and research. I see a washington 15 cent perforated 12 with a double line watermark( a backward S), on bluish paper. Surely it couldn't be a (382 printed 1911 with a single line watermark) because of the 1910 cancel?

Welcome.
What leads you to believe that it is a blue paper variety?

Have you tried scanning the stamp against an orange background? This helps ID the grayish cast to the paper.
https://goscf.com/t/41087

Here is a blue paper example (stamp on left with grayish paper color)


Don

Bluish paper is not blue. Tricky. Needs study. Show a scan of the reverse.

Front and back against orange background beside another 15 cent Washington.

Is my opinion correct about the stamp not being a 382?

The stamp is toned, but not a bluish paper. FYI-the watermark is too weak to be a bluish paper as well, genuine bluish paper stamps have very strong DL watermarks.

Bluish paper. Attributed James Dire,

Randy - given that the bluish paper variety has 35% rag, are colored fibers visible front or back under magnification?

Shermae a good question. In this case I would prefer to defer to those more experienced with bluish paper.

For whatever reason when I put the stamp in watermark fluid the very first time the water was extremely strong, it stood out and was very distinguishable. But since then its been harder to see, I've placed an order for another brand to see if it makes a difference. It was just recently that I ran into info stating that the watermarks show very strong on the bluish paper stamps. Its one of the main reasons I was convinced it was indeed a 366. Then again I'm puzzled by not getting the same results trying yo get that watermark to pop.