Accompanied by the Extract from the Archives.Ref. 2497 and 2438-1From 1951 to 1963, only 179 examples of these two models were produced with the caliber 27-SC Q, bearing the serial number 888'000; the majority were made in yellow gold, with very few in pink gold. Only two were made in platinum, and to date only one is known in white gold, the one being sold in this auction.The platinum watch, made in 1953 (movement 888'029) was sold by Antiquorum Hong Kong, in June 9-10, 1997, lot 199.The Ref. 2438-1 with screwed case back was produced in very small quantities. To our knowledge, only four examples were made in pink gold. One of these four watches was sold by Antiquorum, Geneva, on November 1, 1998, lot 465.Ref. 2497, begun in 1951.- First series from 1951 to 1958 with applied Arabic numerals and "Feuille" hands.- Second series from 1958 to 1960 with applied Arabic numerals and "Dauphine" hands.- Third series with applied gold indexes and "Dauphine" hands.Ref. 2438-1, begun in 1952.- First series with applied Arabic numerals, "Dauphine" hands, fluted lugs, screwed case back.- Second series with applied "Bâton" indexes, "Dauphine" hands, fluted lugs, screwed case back.Similar watches are published in "Patek Philippe Genève, Wristwatches", by MARTIN HUBER and ALAN BANBERY, Patek Philippe, Geneva, 1998, pp. 284-287.Geneva Quality Hallmark.The 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" (or Geneva Quality Hallmark) which are hallmarks representing the Geneva coat-of-arms. Pocket watches or wristwatches which carry the Geneva Quality Hallmark, considered to be equivalent to a "Bulletin Officiel de Marche", stamped on a bridge and on the main plate of the movement, were qualifiedo be officially termed "chronometers".