Protecting oversized 1809 letter?
I have recently come into possession of a letter written in 1809. It had been in a basement for many years, folded up and stored in a metal box. The paper it's written on is quite thick but the letter has been damaged along the folds. It's a very large sheet of paper, maybe 22" square or so. I'd like to put it in a plastic protective sleeve so it can be stored unfolded and also so that it can be read, but I can't seem to find any that are large enough. Anyone have any ideas?