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Help with Mexican Sterling Silver hallmarks

I have a beautiful turquoise sterling necklace that i need some help on. On the back of the turquoise piece that is attached to the necklace reads Loscostillo sterling A-O1 What does A-O1 mean?
On the clasp it reads LJSCostillo or maybe just JSCostillo? Is that the maker? Finally on the other side of the clasp is stamped TA-C1. I have seen TA-O1 but that clearly looks like a C not an O. Would love any feedback that can me. Also would like to know around what era this was.
Thank you!
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now the marks from the clasps
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