I have a set of these hinges (at least, they seem to be hinges) but I'm not sure what they're for.
They measure about 1.5" (3cm) in the longest direction.
Here are some odd features:
No obvious way to attach the parts on the left with the one on the right!
Setscrew in U-shaped piece (second photo)
I assume these would be surface-mounted, they seem too thick to mortise into anything.