Understanding Markings and Authenticity of 22K Gold Jewelry

Question
I have this necklace that has 22KDM AND THE 22KDM IS BACKWARDS I SCRATCHED ON THE STONE WITH 10 ,14,18,22K ACID AND IT WAS CLEAR YOU COULD SEE THRU IT AND THE SCRATCHED GOLD WAS STILL THERE.IF THIS IS REAL GOLD WHY THE FUNNY MARKINGS.THANK YOU

Answer
Sheila, my advice is to keep the acids off of gemstones. Most are not affeted but some might be damaged.

As for the mark being backwards, do you mean like in a mirror with backward letters? If that is the case, I have no way to explain it only the maker could tell us. If the mark is on a thin metal tag or a folded end soldered to the necklace, the gold would have been folded backwards and what you see is the backside of a stamp on thin metal.  If the marks are k22 that is acceptable and not so uncommon. I suspect the DM is the makers mark.

If unsure, have the necklace tested by a reputable jeweler.

God Bless and Peace.   Thomas.