AgAu Jewellery has dated this piece to the 1960s.

Metal: 18ct yellow gold.
Hallmarks: Marked for 18ct gold on the pendant and 0.04 for DIA weight
Stone(s): 1 x faceted blue topaz (5.00ct), 3 x diamond, totalling (0.04ct)
Measurements: Pendant 19mm x 11mm
Weight: 2.7g
Condition: Excellent condition
AgAu Jewellery has dated this piece to the 1960s.
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