Ca. Ø50mm, ca. 83g, 18K gold à-goutte, case number 247280, movement number 388237, extremely rare chronometer calibre, 21 jewels, wolf's toothing, special fine adjusting device, very well preserved enamel dial with extremely rare power reserve indication, blued Breguet steel hands, case with minimal signs of use, in working order. This extremely rare chronometer was actually not intended for sale, but for testing purposes at observatories. According to the archives, it was made in 1920 and not sold until 1939. In the archive documents, the movement is marked 'Development Resort'. Provenance: Antiquorum, Geneva, November 13, 1994, 'The Art of Vacheron Constantin', lot 65, sold for CHF 16,100.