Vintage Gold Filled/MOP Pineapple Round Locket

This is a beautiful gold filled/mop with a pineapple on the mother of pearl. I don’t know what the chain metal is. Given to sweetheart during WWII. Master Gunnery Sergeants wear a distinct rank insignia with a stylized bursting bomb between three gold chevrons and four gold rockers, often jokingly referred to as the “Pineapple Patch” due to the fruit it resembles.