My guess is a hanger of some sort. Military sword hanger? Carbine Hanger? From Indian Wars Era (Post Civil War). The teeth are clearly designed to bite into leather. The hook would most likely hang below that for whatever it held to suspend straight down. The loop below the hook could be for securing the device to something to keep it from swinging freely such as the wearers leg. We call this a WAG back home. Wild A** Guess!!! But it does fit the time when many swords and carbines were being used. I Googled the patent date and came up with nothing. Typed it in many different ways. If you look at buckles from that period you see some things pretty close but no cigar. Whatever it is, I can truely say that it is the very best one I have ever seen!!!
Good Luck
Jim