An early 18th century gold ring set with a foil-back cushion-shaped pink topaz

An early 18th century gold ring set with a foil-back cushion-shaped pink topaz, gadroons to the reverse and with bifurcated shoulders set with rose-cut diamonds, fluted shanks, size K, a George III diamond flower head ring set with six cushion-shaped diamonds (one missing) with bifuracted shoulders, size L, an early 19th century diamond cluster ring, set with nine diamonds and foliate pierced gold shank, size O and a paste-set regency flower head gold ring (damaged), size O 1/2