Art Deco platinum diamond set horizontal plaque ring

Art Deco platinum diamond set horizontal plaque ring. Centrally set with a round Old European cut diamond in a millegrain collet setting, set to top and bottom with two round Old European cut diamonds in marquise collet settings, to a rectangular openwork plaque embellished with diamonds, flanked to either side with integrated diamond set shoulders featuring ribbed terminals before smoothing to a solid shank. Marked platinum and iridium.