Antique Beloved Greyhound Whippet Dog Portrait Brooch

c1900 A hand painted dog portrait of a greyhound or whippet. I didn't open the back up so I am not sure of the material-but under loupe I see brush strokes and in the lighter area-could be celluloid. It is well done and signed FS. 1 1/8" diameter. The brooch frame is gold tone and the back is silver. C-clasp closure. Glass front. Overall it is in very good condition on the front. The back panel looks to have been replaced but is secure.