Estate Vintage Men’s Signet Ring, Signed. Mid-Century Era Onyx and Diamond Gentlemen’s Ring, 10k Gold Band. This ring is crafted in 10k yellow gold with rectangular flat black onyx and bevel-cut accent diamond. Marked “OC 10k” - “OC” mark of Davidson & Son’s NYC, prominent in the mid-20th century for Masonic and signet work. Please note, the center diamond and its surrounding small faceted points have not been assessed for size, color or clarity by a gemologist yet. There are minimal hairline scratches on face of onyx, and there is patina on gold band consistent with its age. Overall it is in good vintage estate condition. Size 12 1/4. All inch/cm measurements can be seen in pictures. A true gentleman collector’s find!