What Is The World Is This Bronze "Coin" ?

Ben;

So it might have had a loop once soldered into it as how else could a big piece of bronze connect to clothing? (Clearly I am not schooled in ancient clothing aside from the fibula etc.)

That's a big nope, Ron.

I agree that it needs cleaning to, hopefully, reveal some details. There's just not enough here to venture anything other than a wild guess. For me that wild guess might be something from Central Asia: Sogd, Mongol issue from Bukhara (some have centralized circles with radiating "arms"), etc. but I have no idea. Can't tell if there's text or imagery of any kind here. Sorry, Joe.

Given the overall form, I will suggest something on the order of a belt applique or harness button, riveted through the center with loop or stud broken off.