Gatsby Jewellery Ltd has dated this piece to the 1920s.
The stone is rubover set in 18k gold, with eight old European cut diamonds (set in platinum) dotted in the surround. Pretty tear-shaped detailing in the under-gallery leads to a D-shaped 18k yellow gold shank.

Accompanied by an independent jewellery report from IGR.
Cut:? Oval cabochon opal and old European cut diamonds.
Colour:? The diamonds are G to I.
Clarity:? The diamonds are VS1 to VS2.
Carat:? The opal is approximately 1.83 carat. The total approximate diamond weight is 1.54 carat.

Circa:? 1920.
Size:? L 1/2 (UK) or 5 7/8 (US). Free sizing available.
Measurements:? The opal is approximately 8.5 x 14.5mm. The head of the ring is 17.7 x 22.5mm and sits 8mm from the finger.
Weight:? 6.73 grams.
Metal:? 18k gold. The diamonds are set in platinum.
Item # 1112313S379
Gatsby Jewellery Ltd has dated this piece to the 1920s.
Gatsby jewellery are a husband and wife team who have years of knowledge and experience in dealing in fine antique jewellery.
You can view the stock and full dealer information on the Gatsby Jewellery Ltd Profile Page