rare Victoria Mexican silver and onyx "mask" Ring

Rings by Victoria of Taxco, one of the few ladies of Mexico's 20th c. Silver Renaissance that are known to us, are such rare finds, they actually touch upon the impossible. If one is really lucky, one might find a shadowbox example from her "angel" parure but I have never before seen a "mask" ring with her signature. Yet here it is - the black onyx "mask" set in elaborate sterling worked such as to represent a headdress and breastplate. Deeply etched and oxidized lines add detail while also bestowing depth upon the silver-work. The patina glows with the warmth only well-loved, well-cared for silver develops and the "mask" looks solemnly out on a world it doesn't recognize any more...

Size / Weight: currently sz 5.5 US yet adjustable thanks to its open shank (please, refer to Condition below); face is 1 1/4" N-S by 3/4" E-W; approx. 5/16" rise; 8.0 grams

Hallmarks / Date: maker's signature as shown as well as "MEXICO TAXCO", "STERLING" and des. no 452; there is no Eagle mark that I can see but I believe this to be a 1948-1958 piece (see below for explanation)

Condition: excellent vintage with great design, beautiful workmanship and silky patina; the "mask" is securely set it its bezel and free of chips or breaks - there is the slightest ever abrasion on its nose but it's not visible to the naked eye and does not affect the ring's presence; I suspect that this ring started its life with a continuous (not an open) shank but a previous owner had it cut to make it adjustable; I have not fully opened it and that's why I think an Eagle assay mark might be "hiding" where the two ends overlap; the intervention is definitely reversible, if you want it taken back to its original condition yet I find it functional and definitely non-offensive

Inv# 15783