New in box 6-curve vintage locket pendant necklace

New in box 6-curve vintage locket pendant necklace Lightweight. Maybe been a child’s gift set. Zigzag engraving in shape of a “6” or curve. 16” simple curb chain, 1 mm wide, almost 1 mm thick 11 mm round locket Box: plastic lid, cardboard box with gold foil trim, soft pinky-beige velvet. New vintage c. 1970s. New in original box. Costume. Silver tone metal and chain. I think they’re steel. Not pewter, not sterling silver. No hallmarks that I can see. Note: is it tarnished? chain and bail are darker in spots. Doesn’t feel tacky or dusty.