Art Nouveau Floral Diamante Brooch

Very much an art nouveau look to this brooch. There is a signature to the back which I have not been able to track. The shape of the enamelled flowers indicate the art nouveau period although sometimes jewellery was produced with a look back to previous era. This is definitely authentic vintage and there is a signature to the back with REG and a signature which looks like SRG but untrackable, so obviously a registered design by by whom ? The design is set in silvertone pot metal with enamelled leaves and flowers and amber crystal touches. Obviously old and in very good condition for all that. Overall dimension is 7cms x 4.5cms. Gift boxed for giving. Proudly supplied by Vintage Online.com.au.