A 19th century opal and diamond brooch, the central old cut diamond set bow encompassing oval

A 19th century opal and diamond brooch, the central old cut diamond set bow encompassing oval cabochon opal, with further diamond set leaf detail applied to bar brooch terminating in larger old cut diamonds, surmounting a conforming opal drop, set in white metal to front and yellow metal to reverse, 6cm wide, 9.3gms, total diamond weight estimated 1.50ct