Art Deco Durand & Co. Sapphire Chrysoprase Diamond and Gold Ring, Circa 1935

An Art Deco, Durand & Co., sapphire, chrysoprase, diamond and gold ring, set with an oval cut sapphire, with a square cut chrysoprase to each side, within two semi circles of eight-cut diamonds, an old cut diamond in each embossed shoulder, mounted in 14ct yellow gold, circa 1935, stamped 14K, with a D maker's mark for Durand & Co., circa 1935.

Durand & Co., 72 E. Kinney St. Newark NJ, c.1915: 49-51 Franklin St. Newark NJ, circa 1896, 1915 and 1934. The D trademark was a horseshoe, with a nail.
From AJU Lang Antiques
"One of Newark's earliest jewellers was James Madison Durand, whose great-grandfather worked in gold and silver in 'Jefferson Village,' or Maplewood, as early as 1756. The young Durand is particularly interesting because of the route he took to become a businessman, starting as an apprentice, then working at the jewellery bench in an already established firm. Finally, he established his own business. A fledgling businessman in the 1830s, Durand, by the time of his death in 1895, had become one of America's leading jewellery manufacturers. His success was attributed by one of his contemporaries as 'plodding work, careful attention to details, vigilant and constant attention to the business, and a superior skill in design and workmanship.' Durand and Co. was located at 49 Franklin St., with salesrooms in New York City at 9 Maiden Lane. Eventually, Durand and Co. employed 125 men".
From knowingnewark.npl.org