Vintage Sorrento 1/20 12K Gold Filled Floral Filigree Brooch Pin. Reddish-brown colored stone. Just guessing, I would say cornelian or coral. There is a tiny black spot on the under side which I didn’t try to clean but tried to take a picture of it.

General information: mid 20th century and later pieces are very often marked 1/20 12K Gold Filled. This means that 1/20 of the metal weight of the item consists of 12K Gold (remember that 12K gold itself is an alloy consisting of only 50% gold – thus a 1/20 12K Gold Filled item is 1/20 12K gold and 1/40 pure gold).