The T in TX-120 stands for Taxco Mexico. The X is for the silversmith. The artist either had a first or last name that started with an X. Yeap that's how they did it. 120 means that the silver smith was the 120th to register with the initial X. No information on the artist. Then I did an internet search that produced no information. Then I hit more research books, auction catalogs and specialty books.
What I found was three designers TX-145, TX183 and finally TX-240. All three (unnamed) designed for various companies in the early and mid- eighties. All registered after TX120. All the clues to the age of this piece scream 80's. (via BlissStreetJewelry) It is also available on (Etsy)