Vintage Marcasite and Silver Brooch

This brooch is marked "Silver" but there is something else engraved/scratched in. It looks like the number 452 and some cursive writing. There are a few of the marcasite stones missing but the ones that are present sparkle unbelievable! I am not sure if it is my imagination but I think that the old marcasite stones sparkle a lot more than the ones one can find in contemporary jewelry.

Thanks for looking:)