Locket

From Memory Alpha, the free Star Trek reference

A locket is a pendant that holds a picture inside. According to human tradition, it is meant to hold a photograph of a loved one.

Tom Paris gave Kes a locket for her second birthday in 2371. It cost him two weeks' worth of replicator rations, and elicited strong feelings of jealousy from Neelix. (VOY: "Twisted")