Take it for what it's worth, but Copilot says it's a
"19th century iron harness/strap adjuster used on horse tack, and the central hole is the giveaway".
I've been playing with Copilot, sometimes it's pretty good, sometimes not so much. Might be a good starting point though.
More from Copilot:
"Your piece has three defining traits:
- Iron construction — WWI web gear buckles were brass or steel with smooth machine edges.
- Two‑slot rectangular body — classic 1800s strap adjuster form.
- Large circular top hole — this is not a military feature; it’s for a riveted or stitched leather attachment tab on horse harness.
This exact configuration appears on:
- Martingale and breast strap adjusters
- Trace strap tensioners
- Saddle rigging straps
- Wagon and farm harness hardware"