This is one of three metal alloy clasps recovered from the Mary Rose, found stored in a small cylindrical box on the orlop deck. All three measured 25mm by c.18mm.
While this one is decorated with a fleur-de-lis, the other two bore the Tudor Rose. On the back is a copper alloy hook, soldered in place. What is unusual about these is that they were typically used by women, suggesting that these may have been a gift for a wife or girlfriend back home.