This brooch is in the form of a spray of wattle, the national flower of Australia, and tea-tree blossom. It was presented to The Queen in 1954 as she toured Australia after her Coronation.
The platinum brooch has yellow diamonds in varying shades to create the wattle spray, and clear diamonds create the remainder of the flowers, in both brilliant and baguette shapes.
The piece was a gift from the people and government of Australia, given at a banquet in Canberra. This was her first visit to the country, and indeed the first visit to Australia by the reigning Monarch.
It was designed and made by Paul Schneller, commissioned by William Drummond & Co and is monogrammed on the back with ‘EIIR’ (see here). The Queen regularly wears this piece, so it seems to be a favourite of hers.