Let's hope it isn't acetate. Acetate is one of the least durable of materials. Over time it warps, discolors, etc.
When I was working at a maritime museum (many years ago) I discovered a plywood box full of WWII Navy recognition models on 1/500 scale. These weren't the usual warships, which were cast in a lead alloy (which is bad enough in terms of preservation and conservation); these were representative merchant ships, and they were cast in acetate or something similar. The first thing I noticed when I found the box was that a strange, syrupy yellow material was oozing out of it. When I opened it, I was greeted by a staggering smell of vinegar. The little models looked like bananas; they were warped beyond recognition. We had to give up and throw them out.
There are all sorts of cheap sources of clear plastic. You can buy real luxurious sheets in various thicknesses at a good hobby shop, or salvage a scrap from a clear plastic package of some sort. And I love the shirt collar idea.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.