Decoding a 10K Gold Ring: JCM Stamp & Stone Identification

Question
I was given a 10K gold ring with the marking JCM in the band.  What does JCM stand for?  Also, I was wondering if it is likely the clear faceted stone was a diamond, because I didn't think they were put in 10K gold rings.  Without having the hardness tested is there any way to tell?

Answer
HI LINDA,

MORE THAN LIKELY THE JCM STAMP IS THE MANUFACTURERS STAMP.YOUR RIGHT THEY DON'T USUALLY SET DIAMONDS IN 10K GOLD. A GOOD GEMOLOGIST COULD TELL YOU IF IT IS A DIAMOND JUST BY INSPECTING IT OR TESTING IT. MOST JEWELRY STORES NOW ARE EQUIPPED WITH ELECTRONIC DIAMOND TESTERS.

THANKS
PETER