Either it would have a little charm like thing near the clasp with it stamped on or it would be stamped on the back of the cross or on the back of the earrings, anywhere really where it could be stamped but it shouldn't be hard to find just stamped so small you have to be near sighted or young to read it.
This is a very pretty set. How long is the chain? Is it stamped? Are the stones cz's they look very sparkly. I thought I was going to stop collecting crosses but your set may change my mind. Really nice auction. :)