Have found photos of a few similar style brooches on-line (different crests and different coloured torches).
They are simply describes as "reversed intaglio " style , possibly Victorian era.
"VINTAGE 3PC VICTORIAN JEWELRY SET Features : Glass reverse intaglio with a painted crest center Griffin accents Set includes a pair of clip on earrings, brooch and bracelet Brooch"
https://www.worthpoint.com/worthoped...rse-1387163245