Can Someone Help Me Identify This Proof?

I need some help learning how to identify proof's.

I have quite a few proofs and a copy of Scott's Specialized catalog that lists all of the proofs, essays, etc.

However I can't for the life of me make sense of how to properly identify them.

There are usually ten different paper types, a handful of die and plate variations, and whatever whatever.

For example this is a Scott # 219D proof. (I'm pretty sure lol)

The best fit that I found is 219DP5 however that is titled "2C lake plate on stamp paper, pair 80$". This is not a pair but it looks like stamp paper to me. There is no entry for just a single stamp unless it was one of the other paper types. I have no idea what india, white wove, yellowish wove, and on card. How do you identify those?

What do you think I have here??
The options are
2c lake large die on india paper
2c lake RA sm die on white wove paper
2c lake PP sm die on yelsh wove paper
2c lake plate on india
2c lake plate on card

or what I thought it was 2c lake plate on stamp paper, pair (but its not a pair so what the heck!!)

Also on the back there is a sort of watermark??

And maybe even was gummed? Or at least has some darkening compared to the front.

Since you say it appears to be on stamp paper, and it has some or part gum, my first assumption is that it was once a jumbo margined regular stamp that someone cut off the perfs to look like an imperf or a proof.

It could also be a single of the 220P5 (or maybe 219D. It doesn't look dark enough to me to be Lake but could be).

The India Paper P3 proofs are on a thinner paper than regular stamp paper, almost like tissue paper.

The Card proof P4 proofs are on a much thicker paper, like cardboard.

The P1 P2 proofs can usually be identified by having much larger margins than the P3, P4, or regular stamps. Post pictures if you think you have some of these.

If you have a lot of proofs, the P3 and P4s are the most common and you should be able to identify those easily. The P5s on stamp paper are usually found in pairs or blocks, but there's no law that says someone can't cut a pair in half so that's possibly what you have. Expect the value of a single to be somewhat less than half the pair price since there is less demand for them as singles.

The picture make it looks more carmine but in person it is very lake.

The margins are quite large so I wouldnt think someone could cut off the perfs to make an imperf?

The back is gummed. I thought it was discolored but after looking again its gum.

The paper is not "stiff" like cardboard, it is maybe only slightly stiffer then normal stamp paper. Its not any thicker or thinner then a regular stamp.

If you look at the bottom perf, it's not in a straight line. This could be someone cutting apart the pair to make two singles? So some momo in the past cut the proof pair into singles....?? Neat...

People are so destructive..