Karat stamp question


I am trading a pearl from a ring to a pendant for a customer. She
has supplied both the ring with pearl and pendant with worn pearl.
Was looking at her ring and pendant, which she got in Korea. The
inside stamp on the ring is a K in a circle, which I assume is
trademark. The number next to it says “75%”. Is this a stamp meaning
18k or is it meaningless? The pendant is stamped 750.

Thanks, Melissa

Yes, 75% is the gold in 18K