Understanding Jewelry Markings: 10K Gold & 'AT' Symbol

Question
Hi Les, I recently inherited my grandmother's rings after her passing and on 1 ring it has 10k on the 1 side and also a symbol AT with a line above both letters on the other side.What does this mean?

Answer
please read previous postings it will answer your question further....this seems to be a popular question among members...
the 10kt is the gold content  41.7 pure gold the and balance are alloys...the other symbol is the original manufacturers symbol....by law a mfg. must mark their creations.
all the best
Les