Pave diamond or cz heart pendant necklace--hallmark will help me figure it out

by Shanna
(Portland ME)

I just got a pendant necklace and the stamp on the gold chain is 1/20 12K which I understand is 1 20th of the gold is 12 k...and there is another mark which looks like a right triangle--but going in the opposite direction--and what looks like the letter S. There is a stamp on the backside of the heart that I cannot read. The stones behave like diamonds but I'm not sure if they are or not.

The size of the stones (each is a little different looking) is maybe 1/16 ct and there are 37 stones.