It measures a fraction over 2in (5.5cm).
Modelled as a specimen tree standing in a detachable square tub, the tree is set with a carpet of brilliant-cut diamonds with calibre-cut buff top rubies to one edge. The tub is set with brilliant-cut diamonds to the centre, baguette-cut diamonds to the stiles, and cabochon rubies to the terminals.
Brooches on this theme were popular from around 1920 and were made by a range of top French makers including Cartier, Lacloche and Henri Picq.
Although apparently unsigned, the brooch is very reminiscent of Cartier's design, choice of stones and execution.
The engraved numbering 2813 on both the tree and tub is also typical of that used by Cartier on their jewellery.
Estimated at £3000-5000 for the evening sale on December 12, it sold for £22,000 (plus 17.5% buyer's premium).