circa 2005, model number 52 N6 1460.1, serial number 1312906, the signed rectangular black dial, 20mm wide, upper half with pink circular minute track, pink single hand and digital trapezoid jump hour aperture at 12 o'clock, the lower with subsidiary circular date indicator and offset running seconds register, signed but unnumbered 17 jewel mechanical crown wind movement, decorated with 'The Côtes de Genève' and with date adjusting pusher below the crown, convex case, 30mm wide, front bezel polished, verso with 4 screws and exhibition back, the border engraved 1312906 DELIRIUM - LA NUIT ASIS SWISS MADE 18K together with Swiss national mark and convention marks for 18ct gold, to the original signed black alligator strap, the signed pin buckle with Swiss national mark and convention mark for 18ct gold‘Delirium’ was a line of ultra-thin watches, first introduced in 1979, and marketed by Concord, Eterna, IWC, and Longines. By the mid-1970s, Japanese watch companies were producing thin, reliable quartz movements and the Swiss companies were being left behind in terms of technology and sales. American businessman, Gerry Grinberg, responsible for Piaget’s ultra thin mechanical watches, had seen his market share eroded by Seiko and Citizen who had introduced ultra thin quartz watches, thinner than any of his mechanical versions. He approached Swiss watchmakers, challenging them to make a world-beating ultra-thin movement before they lost the entire market to the Japanese and offered 2 million Swiss Francs if they could produce an ultra thin quartz movement for use in his Concord watch brand. On January 12th 1979, four Swiss watch companies - Concord, Eterna, IWC, and Longines - announced the world's thinnest watch, just 1.98 mm thick with the movement built directly into the rectangular watch case. The watch was branded ‘Delirium’. Concord used the name for their models, which were focused on the American market, with the other three companies branding under different names. Further versions were produced, all with quartz movements, including the Delirium IV, which, at just 0.98mm thick, remains the thinnest watch ever made. In 2005, Concord introduced a mechanical Delirium model – this example – which, although much thicker than the original, still retained the same distinctive style and rectangular case of the original quartz versions.