Identifying TAXCO Sterling Mark MMR + Symbol

[memo]

We have a pair of sterling screw-back earrings, with inlaid lapiz and green stone.
Mount of one screwback is marked 170 (possibly the model number?).
Mount of the other is marked (faintly in parts) - what appears to read: MMR and TAXCO 925 MEXICO.
At the top (knob) end of the screwback is marked: STERLING and a stylized infinity-like mark/symbol. Does this mark/logo belong to a Taxco silversmith? Any ideas who the maker is?