Vintage Amber toned necklace / brooch gold tone trident marked pre 1970s

This necklace is about 16” in length The pendant is huge and doubles as a brooch Across is over 2.5” Marked with a trident over an M I looked and cannot find a maker but is def 1970: or earlier Excellent condition I’m not sure what the stone is if it’s glass or a stone or even plastic it’s gorgeous though