Vintage white onyx Aztec sundial 24 inch pendant necklace

This is a vintage necklace from an estate purchase in excellent like new condition.  White onyx beads and medallion pendant on a 26 inch necklace. Not sure what metals are but gold and silver toned is all I know of. Definitely not precious metals. Aztec sundial face type on the medallion. Not sure of the era but guessing 60s-70s. I believe this was made in Mexico. Reasonable offers considered