There was a range of these lovely brooches manufactured in France in 1920's and generally no signature to the back. There is actually a name imprinted fairly indistinctly to the back of this one which reads AZAIS.   This is a fairly common French surname.  It may have been the name of the original manufacturer, or it may be the original owner of the brooch had the name inscribed.  Dimension across is almost 5cms. An art deco design centred in a marcasite frame. In very good condition considering its age. There is a well working trombone clasp to the back.  Gift boxed by Vintageonline.