Rare Vintage Diamond Ring

GUC Rare Vintage. Minimalist. Estate Find. (.08 ctw) Criss-Cross Shank, 21K(ct) Yellow Gold Band,  3 Stone Diamond Promise Ring, Size 3 1/2. Markings Slightly Faded And Apparently Melted And Smudged, But Readable, 21 ct Not Sure Exactly What The Markings Mean. But After A Lot Of Research, I Could Only Come Up With The Following. **After Inverting The 2 pictures That Show The Markings. I Can Clearly See 21 ct Engraved In The Band Of The Ring.