AgAu Jewellery has dated this piece to the 1920s.

Metal: 18ct yellow gold with Platinum setting
Stone: Carat a lovely bright sparkly diamond (0.30ct).
Colour H.
Cut Brilliant Brilliant Cut
Clarity SI1 clean to naked eye, couple of tiny specs through jeweller's loupe
UK Size: L
Hallmarks: Marked for 18ct/Plat
Weight: 2.5g
Condition: Excellent condition
AgAu Jewellery has dated this piece to the 1920s.
Agau jewellery offer an extensive range of 9ct and 18ct gold jewellery.
You can view the stock and full dealer information on the AgAu Jewellery Profile Page