Priest Finds Ancient Object In Church Cellar, Then One Of The Nuns Tells Him This

The Disc

As he unwrapped the old fabric, it crumbled in his hands. Inside was a large bronze disc, tarnished but solid, and clearly very old.

Michael saw strange engravings running along its rim. He traced the markings with his thumb. They were neat and carefully edged in, clearly done by a professional. But what was it?