An art deco diamond wristwatch, by Cartier, circa 1925. Photo Bonhams

LONDON.- A stunning art deco diamond wristwatch by Cartier circa 1935 that belonged to Eleonora Sears, the great, great granddaughter of Thomas Jefferson, will be offered in the Fine Jewellery sale, taking place at Bonhams London on the 21st September.

The strap consists of baguette and brilliant cut diamonds and is estimated to sell for £15,000 – 20,000. As well has her famous great, great Thomas Jefferson, the principal author of the Deceleration of Independence and the third President of America, Sears was a pioneer of American women's sport. Popular among the upper class circles of New York and Boston, Seers frequently topped New York's '10 best dressed' list. After meeting her in 1924 Prince Edward, the Prince of Wales, said she was his favourite dance, squash and tennis partner.

An art deco diamond wristwatch, by Cartier, circa 1925. Photo Bonhams

The rectangular dial with Arabic numerals between courses of baguette and brilliant-cut diamonds, to an articulated pierced baguette, single and brilliant-cut diamond strap,diamonds approximately 6.05 carats total, dial signed Cartier, strap signed Cartier London, length 17.2cm - Estimate: £15,000 - 20,000, US$ 25,000 - 33,000

Also included in the Bonhams sale are pieces of jewellery by Black Starr & Frost, America’s oldest jeweller. Throughout the long history of the Jewellery House, with numerous name changes, the firms enduring designs and exemplary workmanship have ensured that it is still regarded as one of America's most prestigious jewellers.

A diamond collar necklace circa 1935 is estimated to sell for £30,000 – 50,000. The articulated collar consists of overlapping triangular plaques set throughout with brilliant and baguette-cut diamonds weighing 35 carats. Estimated at £3,000 – 5,000, a rock crystal and diamond necklace attributed to Black Starr and Frost circa 1930 is another highlight of the sale.

A diamond collar necklace, by Black Starr & Frost. Photo Bonhams

The articulated collar of overlapping triangular plaques set throughout with brilliant and baguette-cut diamonds,diamonds approximately 35.00 carats, signed BS & F, maker's mark in a lozenge, one diamond deficient, length 39.0cm - Estimate: £30,000 - 50,000, US$ 49,000 - 82,000.

Note: Black Starr & Frost is America's oldest jeweller. Originally founded in 1810 under the name Marquand & Paulding, the firm formed numerous partnerships. By the 1860s, the firm was trading under the name Ball Black & Company and was regarded, along with Tiffany and Gorham, as one of the leading jewellers in America. In 1876 the firm moved to Fifth Avenue and changed its name to Black Starr & Frost where it continued to trade until 1929 when it merged with Gorham to become Black Starr and Frost-Gorham Inc. At the 1939 World's Fair held in New York they showcased bold sculptural designs typical of the period. Throughout its long history and numerous name changes, the firms enduring designs and exemplary workmanship have ensured that it is still regarded as one of America's most prestigious jewellers.