Truly an archetypal model, reference 1518 was the first perpetual calendar (with moonphases) chronograph wristwatch ever produced in series when it was launched in 1941, in the midst of World War II - a bold timing to say the least. According to research, only 281 examples were manufactured, in yellow and pink gold and a few examples in stainless steel, until the reference ceased production in the early 1950s. Not only did it set the design elements used by Patek Philippe in all of its subsequent perpetual calendar chronograph wristwatches down to today’s ref. 5270, but in its own manner greatly contributed to the manufacturer's dominant position in the watchmaking industry. Consider for example that no other company achieved a serial production of similarly complicated pieces until the 1980s. Its successors are references 2499, 3970, 5970 and finally 5270, which features an in-house movement - this make the present line of watches the only one with ongoing production at Patek Philippe since the 1940s.

Over its course of production, the ref. 1518 can be broken up to specific batches that were manufactured over the years.

It is estimated that:
1941 – 1942 = 18 examples made
1943 – 1944 = 36 examples made
1945 – 1946 = 36 examples made
1947 – 1948 = 60 examples made
1949 – 1950 = 56 examples made
1951 – 1953 = 75 examples made

Out of the 281 examples of the reference manufactured, it is believed that 215 examples were encased in yellow gold with 58 examples made in pink gold and 4 known in steel.
It features a 35mm diameter Calatrava-style, Bauhaus-inspired case. Gold cases were made by master casemaker Emile Vichet identifiable via key no. 9. The case architecture slightly changes from early (1941 – 1945) to later (1946 – 1953) examples: early cases feature a flatter appearance with a smaller crown and the positioning of the pushers was slightly higher. Later examples of the reference had lugs that were slightly more tapered, the crown is larger and the chronographic pushers sit lower. Usually with a silvered dial with applied gold Arabic and dotted numerals, the dials were manufactured by Stern Frères featuring engraved/enamelled graphics and an enamelled gold moonphases disc.

The present example is a stunning representative of this legendary reference. Boasting absolutely unmolested and vibrant graphics - without losses or fading - the dial furthermore sports very sharp edges to the day/month windows and moon phase aperture.
The case is in highly appealing condition, sporting thick and balanced lugs with the the two hallmarks not only visible but very crisp and deep, one stamped on the band and the other beneath the lug.

This remarkable specimen has been missing from the public market for about 20 years, as it was last sold in Geneva in June 2003. Its first appearance goes however back more than 20 additional years, to 1979 in New York. It would not be surprising if collectors had to once again wait a similar timespan before this piece appears for a third time.

Given the increase of public interest in these early masterpieces of watchmaking, acquiring such a remarkable specimen is destined to become an ever harder endeavour, thus rendering this one an unmissable opportunity for the serious watch collector.