Well this is a fascinating thread to stumble upon! I have not a medal / medallion, but rather a cast and stamped pewter dish with the exact image of Petrarca that appears on the Ambrogi medallion. The details on my dish are well worn, but a close comparison of the Ambrogi bronze and my dish show an exact match, including size, the depressed area on my dish being 15.5 cm.
More detailed large photos of the dish are in my Google album at https://photos.app.goo.gl/Jze27ha1devMvgCv8 Several folks versed in Renaissance art speculated that it was an alms dish from a church, based on the wear and scratch patterns as well as the overall theme.
Constanius doesn't appear to have been here for some years, but if anyone here knows him please let him know about it.
I'm very curious whether anyone here might have some insight into the age of this piece and how it came to be. I will post the Ambrogi medallion from the Hall Collection sale in a moment for comparison.
