Gatsby Jewellery Ltd has dated this piece to the 1930s.
The stone is secured in a platinum six-claw coronet collet and sits on a slender 18k yellow gold shank set with eight (four each side) eight-cut diamonds in the shoulders.

Accompanied by a Natural Diamond Identification Report from HRD Antwerp (#180000033461).
Cut – Old European cut in the centre. The diamonds in the shoulders are eight-cuts.
Colour – H in the centre. The diamonds in the shoulders are F to G.

Clarity – VS2 in the centre. The diamonds in the shoulders are VS1 to VS2.
Carat – 0.49 in the centre, with approximately 0.06 carat in the shoulders.
Circa – 1935.
Size – L 1/2 (UK) or 5 7/8 (US). Complimentary sizing is available, can be sized up or down.
Measurements – The diamond is 4.81 x 5.00mm. Sits 6.1mm from the finger.
Metal – 18k yellow gold and platinum. Tested.
Gatsby Jewellery Ltd has dated this piece to the 1930s.
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