10k yellow gold pendant

This was a Christmas gift from my mom last year. She's had an interest in jewelry long before I did and has even started making her own. It has a couple marks that I'm curious about and hope maybe someone can help me figure them out. The inside of the pendant is marked 10k SUN, the clasp and the part it connects to are both marked 10k but one is marked N.C. I'm honestly not sure if they're diamonds not even sure if there's a way to find out other than maybe taking in to a jeweler. That parts not all that important, I'm just curious about the Mark. I would love a secret decoder ring to figure out mystery marks:)