This watch is extremely rare for it bears an original black dial and is the only one known to date with this particularity.Ref. 2499Produced in 349 examples from 1950 to 1985, with the calibre 13??? CC, among which are very few with tachometer, the majority in yellow gold, rarely in pink or white gold.- First series from 1951 to circa 1960, square buttons, ?Feuille? hands, applied Arabic numerals, fluted lugs. A similar watch is published in Patek Philippe Wristwatches, by Martin Huber & Alan Banbery, 1998 Edition, p. 304.- Second series square buttons, ?Dauphine? hands, applied indexes, the 12 in Arabic numerals.- Third series from 1960 to 1978, round buttons, crystal glass, ?Dauphine? or ?Feuille? hands, applied ?Bâton? indexes. Very few examples were made with tachometer or telemeter scale, some of these have applied Arabic numerals.- Fourth series from 1978 to circa 1985, it becomesRef. 2499/100, with the calibre 13??? CCR, round buttons, sapphire crystal, ?Dauphine? hands, applied ?Bâton? indexes. Very few examples were made with tachometer or telemeter scale, and three examples only with sapphire crystal back. A similar watch is published in Patek Philippe Wristwatches, by Martin Huber & Alan Banbery, 1998 Edition, p. 302. Two examples are known to date in platinum, one was sold by Antiquorum, Geneva, on April 9, 1989, The Art of Patek Philippe, lot 34, for SFr. 418?000 (US$ 253,300).Poinçons de GenèveThe voluntary quality control of watches at the Geneva Observatory, was established by a law dated November 6, 1886. Conditions were laid down for the attribution and stamping of the Poinçons de Genève, punch-marks designed as the coat-of-arms of Geneva. Pocket watches, or wristwatches which carry the Poinçons de Genève, considered as an equivalent to a Bulletin Officiel de Marche, punched on a bridge and on the main plate of the movement, were qualified to be officially termed ?chronometers?.