I have had two of these shackles for years. I have never really known what they are.
I have thought they might be handcuffs of some sort but they are only approximately
Two inches inside. I found one online but they said jail lock or chain link. I can't wrap
My mind around that either!
Thanks, Bill D.

Looks like it could be to connect leg irons for chain gang.

Possibly to restrain a farm animal (goat,sheep?) while being sheered, milked or having some health related care.

Thanks for the ideas! We have had quite a few discussions about what they were for and have speculated about the same ideas mentioned. I'm just confused as to their purposes and really curious! Thanks again, Bill Davis

Looks like a pipe hanger.?.!

There are all kinds of them, many cast.

Chilly