Pocket watch: extremely rare Cartier "Couteau Ultra Thin" gold/enamel dress watch, aristocratic property

Ca. Ø46mm, approx. 43g, 18k gold, extremely flat, beautifully enamelled case, blue engine-turned enamel with white rim, platinum monogram GB on the back, set with diamonds, serial number 2493, extremely flat precision lever movement signed Cartier, engine-turned, signed dial, Breguet steel hands, in working order, in good condition, extremely rare. The watch comes in a later Cartier original box. It comes from the same aristocratic family as lot 4122, but has the owner's monogram with diamond setting instead of the aristocratic crown. Comparable Cartier dress watches have achieved international prices of between 20,000 and 30,000 Swiss Francs/US dollars: source: https://www.cortrie.de/go/JAe