🔎 UNIDENTIFIED Military rivet button?

[cudamark]

It's like a jeans fly button by the looks of it, but, I've never seen one before. 15mm across. Any help with usage and age?

 

[pepperj]

Saw nut for a hand saw.

 

[Rmeav8r]

If that's the US Army Great Seal it might be a cuff link or possibly part of a bridle or harness rig.

 

[cudamark]

After a bit of cleaning, it's looks like the remains of a screw back, like what they used on their collar insignia. I didn't realize they used that sort of insignia on a collar....did they?