Kentish composite brooch

Composite silver and gold disc brooch, diam. 5cm. Backplate silver with rounded light-and-shade decorated rim, and inner border flat band with row of small punched annulets and gilded. Central area slightly dished and set with gold cloisonné cells which have all been riveted through backplate. At centre a circular cell with 3 radiating triangles, all in one group, and framed by soldered beaded gold wire. In central cell a white boss cut out to be inset with a cabochon garnet, which in turn has inlaid into it a blue glass opaque ring. The triangles were set with garnets, 2 missing, remaining one flat on gold foil backing. Near to points of triangles, tiny gold round cells with beaded gold wire collars, 1 set with sunken cabochon garnet, 2 with flat. Interspaced between are medium sized cells, without wire collars, but with shell bosses set with tiny round garnets, 1 flat, 1 cabochon, 1 missing. Remaining surface area of dished middle of brooch covered by disc of sheet gold with beaded wire border, and covered with filigree work. This in beaded wire. Around edge double row of tiny annulets, except on one side where pattern has slipped. Single row of annulets around each cells. Remaining area covered with pelta and occasional figure-of-eight work. The gold plate is damaged, and torn, revealing paste beneath. Evidently this is antique because tiny rivets have been used, partly concealed among annulets, to peg down the damaged parts. These rivets show on back. Some of filigree has been lost from surface, and the rest badly worn. Rim also heavily worn. On back, the silver pin hinges in a hollow cylinder, into which it is pinned by an iron rivet, and which itself is attached to back by a disc riveted in 3 places, but one empty rivet hole suggests it may have been re-attached at some time.Order of construction: pin mechanism riveted to back plate, then cloison cells to front. Only after that were settings and filigree work added. Much damaged, and obviously old when buried.