It Appears to be a well worn silver strike that has seen many days in someone's pocket and handled alot, silver tarnish's
just like the picture of it shows, The Ceasars pewterlike strike has the same apearance,,,and I assume they etch them in a silver etching soloution that speeds up aging, thus giving it the grey/black color.. I,ve aged a "silver ring" in the same way, back in my college days learning metal smithing techniques..
Have a Great Day!!!

Gabe & Carol on the Detroit River, Michigan