✅ SOLVED Guesses on what this might be?

[Mason Jarr]

Another of the finds from an Indian Wars fort site. I'm pretty sure it's made from pewter which makes me think it was the back of a buckle or maybe a rosette. There is some detail of scroll work if you look closely. The back appears to have two solder marks on it.

 

[The Rebel]

I'd say bridle rosete.

 

[GlowingArtist]

A mid 20th century bottle cap that was run over by a train or other flattening asphalt machine?

 

[ANTIQUARIAN]

As Rebel suggested, it's likely an early horse rosette based on the remains of iron mounts on the back.
Very nice find,
Dave