Sterling Silver Rectangle Pendant w/ Amber Stone on 19" Rope Chain Vtg Necklace

Pretty sterling silver rectangle pendant with an amber colored stone with a matte finish. I do not know what kind of stone it is, if it's real amber or something else. Has a small marking that I can't identify. Pendant and necklace stamped 925. Rope chain is 19". nice vintage condition. Total weight 5.2 grams.