My Mom brought this piece back from Italy when I was 13, which makes this brooch nearly 60 years old. It is not filigree, but a type of work called CANNETILLE, a type of metal decoration in the form of coiled thin wires, often with tiny beading, to form a filigree-like pattern, and named after a form of embroidery. It was most popular in the late Georgian era, but continues to be produced today. This piece doesn't have any beading, but the fine wirework is superb. The brooch has three layers but only the two open layers have the enameling in a soft green that turns to gold towards the center of the flower. The brooch measures 2 1/16" in diam. and has a working safety clasp, and below the clasp there is a tiny square on the back of the brooch which is stamped 925, but you need a loupe to read it, so I did not try to photograph it. It comes in the original box from Padua, Italy.
(I have included a pic at the bottom of a Georgian piece of cannetille jewelry with gemstones)