What is the true age of "CORO" jewelry?

by Mary Danzer
(Livingston, Montana USA)

I have a pin with the jelly belly pink pieces in it, on the back it only says CORO nothing else, how do you know the age of this pin or if Gene Verrecchio is the maker or if Adolph Katz is the maker?

What marks would define which artist made a piece? Please help.