Jewelry such as this is referred mostly as WW2 era sweetheart jewelry. If you do a search as such you'll find many examples with the US military branch insignia on them. Young women and mothers would where this as a memento to a person they knew who was in the military and the branch they're serving in. I believe they were very popular in both the US and Britain.They were made very inexpensively to higher end pieces made with precious metals and gem stones.