Nice find, congrats. Have you checked under & around all the areas for hair? Odd question, but there could be an original strand there somewhere. Sort of reminds me of very old photographs or paintings that have a backing on them, then behind that is the artwork. Sometimes if slit open, there's a letter or other item taped, or something written by the original owner or person who framed it. I'd also be curious to put a black light or a UV light on the hat to see if traces of blood, etc. would show up. Maybe I read too much Nancy Drew.