BUCHERER ring with 3 square-cut diamonds

BUCHERER ring set with 3 carree-cut diamonds totalling ca. 0.20 ct, ca. WHITE (H)/VS and 6 carree-cut sapphires totalling ca. 0.40 ct, 18K YG, 3.1 g, ring size 53, 20th/21st century, very minor signs of wear, maker's mark.