This appears to be a slave collar?? Any guess to the value? Not sure that I will sell it but am considering donating to a museum. It makes me uncomfortable having it in my house.
1st - Welcome Aboard to both of ya! You didn't list your state (or country) in your profile. So, you might consider jumping over to Sub-Forum: Select Your Area.... for information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country).
2nd - Maybe a Jailer Iron Shackle or perhaps a Prisoner Handcuff?
I would think it would be rounder too, like your neck, not oblong. Maybe a gate latch if 2 posts would fit inside it. That's just my guess. Ranchers come up with many different varieties of gate closures.