Sterling hallmark on Turquoise Ring Jb? Jab? Jp?

[annatorr]

I have this turquoise ring made of sterling silver. I believe it is Native American however its possibly Mexican or South American. The hallmark is the word "STERLING" written in a circle with a symbol that I believe to be initials. Possibly Jb or Jp. Or perhaps Jab, Jap, Ab, or even a fancy A. Does anyone recognize this? Images below.

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[tatsnbikes]

Jane popovitch Navajo shop mark