Gatsby Jewellery Ltd has dated this piece to the 1920s.
The diamond is mounted in a classic six claw platinum collet with an open gallery, leading to 18k yellow gold shank.

There are some visible inclusions in the diamond. Because we use a macro lens, the inclusions look worse in the photos than they do in person.
Contemporary hallmarks, London.
Cut – Old European cut.
Colour – G.

Clarity – I1.
Carat – 1.03.
Circa – The diamond is circa 1925.
Size – M (UK) or 6 (US). Complimentary sizing is available, can be sized up or down.
Measurements – The diamond is 6.8 x 6.5mm in diameter and sits 6.1mm from the finger.
Metal – 18k yellow gold and platinum. Hallmarked.
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