The Drapers’ Company is one of the livery companies, or trade associations, in the City of London, and the Queen is its Freeman. As such, she has this special badge to wear as a brooch for related engagements.
The Drapers' Company Coat of Arms
The badge is mimics the company’s coat of arms, which depicts “three sunbeams issuing from three flaming clouds crowned with three Imperial crowns of gold on a shield of azure”. The blue background looks to be enamel, with detailing in gold and a glittering surround. Framing the oval are words, likely the company's motto, "Unto God Only Be Honour and Glory".