The jewelers mark means it has just been marked by a certain person. Think of it this way a brand you brand cows with is a mark of a farmer so he knows what cows are his. That is what a jeweler does.
It probably indicates gold plate.
HDS is the maker's mark for Helzberg Jewelers.
Most likely it is Gold shell (gold plated) But it could be a jewelers mark.
This mark refers to wholesale jewelers H Nathan and Co of Fore Street, London.
It is the makers mark for Sandeep Diamond Corp. in New York, NY. They are wholesale jewelers to the trade.
GDM Jewelers is the name of the company that made the necklace.
It's 10 karat gold, and AAJ is the designer or band maker.
The 10k identifies the metal as 10 karat white or yellow gold. Ud is probably the jewelers mark such as Ultra Diamond.
Just a guess , possibly a jewlers mark? <><><> Think that is a good guess. The mark, known as a Jeweler's Touch, is their registered trademark. Very possible that is the touch for Zales jewelers.
special trade mark
SLK stands for Salt Lake City jewelers. Which is a fine Jewelers Hallamark !
p4 is a blend of silver, gold, platinum, and palladium. Looks a lot like white gold but just does not have the luster. sr is most likely the jewelers mark.