Sterling Snowflake Obsidian Fish Brooch signed Allison

Fun vintage fish brooch in sterling silver set with a large stone that I believe is a snowflake obsidian. The stone is mottled black with kind of fuzzy gray spots. I love the raised features of the fish and the applied rings decorating his tail. He's nice and large, at 2 1/2" x 1 1/4". Marked on back "Allison" and "Sterling". There's some heavy tarnish in places but very nice vintage condition with no issues. Great gift for your favorite fish lover or fisherperson!