I have one that and old time turkey hunter's son gave me a few years ago. The lip of the box was concave from where that old fella wore that thing out. I never used it hunting.
He also gave me what looks like a box call base, but it has a 16d nail sticking up right in the middle of it so that the head just protrudes above the brim of the box. Then there is a separate piece of rectangular wood (maybe 5"x3" and about 1/2" thick) that you use to rub/scrape across the nail in the box. I wish I knew the proper way to hold the thing, because I never could get a decent sound from it.