Gatsby Jewellery Ltd has dated this piece to the 1920s.

Accompanied by an independent jewellery report from IGR (#30309528).
Cut –Old mine cut.
Colour – I.
Clarity – SI2.
Carat – 0.97.
Circa – 1925.
Size – L 1/2 (UK) or 5 7/8 (US). Complimentary sizing is available, can be sized up or down.

Measurements – The diamond is approximately 6.2 by 6.2mm and sits 6.9mm from the finger.
Metal – Platinum. Tested.
com/560791438
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.
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