Marcus and Co. diamond brooch. Set to centre with one round old cut diamond in an open back grain setting with an approximate weight of 0.40 carats, further adorned by sixty round mixed old cut diamonds in open back grain settings with a combined weight of 2.45 carats. The total approximate diamond weight is 2.85 carats, to an elegant brooch featuring intricate filigree work with millegrain edging throughout, a decorative gallery with scalloped and chenier detailing, and fancy open shape backholing, fitted to reverse with a secure pin and safety catch, approximately 6cm in length. Tested platinum and iridium, signed 'MARCUS' for Marcus & Co., American, circa 1915, accompanied by original Marcus and Co. box.

The American jewellery firm of Marcus & Co. was based in New York City and is best known for their high-quality Art Nouveau and Art Deco pieces. The company was founded by Herman Marcus, who was born in Germany where he trained at Ellemeyer, the court jewellers in Dresden. It was in Europe that he learnt enamelling techniques which were not common in the US at that time, and this expertise led to his first job in New York, with Tiffany & Co.

In 1864 he started his own firm, a partnership with Theodore Starr, forming Starr and Marcus, and though highly successful, the firm was dissolved in 1877. In 1884, Marcus became a partner in the firm Jacques and Marcus, where his son William was already a partner, and in 1892, when Georges Jacques retired, the firm became known as Marcus & Co. By this point, Herman Marcus was already well known and respected by the New York City jewellery community.

The firm became known for their Art Nouveau jewels, showcasing their affinity for plique-à-jour enamel work, as exhibited at the 1900 Exposition Universelle. The firm’s bold use of brightly coloured enamel mixed with rarely used gemstones, such as zircon, tourmaline and chrysoberyl, is unmistakable, and represents a confidence in design not usually seen in this period.

Exquisite Art Deco jewels highlight the firm's commitment to quality, craftsmanship and beauty and in 1939 they were one of just five jewellery firms to exhibit in the 'House of Jewels' at the New York World's Fair. The other jewellers to exhibit were Tiffany, Cartier, Black, Starr & Frost and Udall & Ballou, indicating how the prestige Marcus & Co. jewels had achieved, with notable clients including the Rockefellers.

Today, Marcus & Co. are regarded as one of the preeminent American jewellers of the early-mid 20th century, with their pieces highly collectable amongst collectors, investors, and jewellery lovers alike.

This brooch is in excellent condition.