I doubt that it is a decapper, the pin would have to be a
lot longer, thinner, and the radius of the hinge to pin would
have to be longer. I've never seen anything like it, and
my guess is that it has some propriatory use and that it
is a part of some kit, rather than a stand alone item.
But, I'm still young and foolish, so, what do I know ?
My best guess: a device made to put a hole in corn-
cobs so they could be strung up in the necessary.
Uncle Bob