marking on hand amulet charm

by Marta
(California)

I have a carved coral hand set in 18k gold cuff with bail stamped 18k on one side and a star 420 or 428 on other. On the cuff that holds the coral hand (clenched with thumb protruding between index and third finger) is a stamp that I think says EC, but I'm not sure if I am looking at it upside down. Another possibility is PC. Does anybody have a clue? Thanks, Marta