Accompanied by Patek Philippe Extract from the Archives confirming production of the present watch in 1943 and its subsequent sale on 10 December 1943.
Reference 1518 was launched in 1941 and according to literature only 281 examples were made until 1954. It was the first perpetual calendar chronograph wristwatch produced in series by any watch company. The model was later replaced by the reference 2499, also a perpetual calendar chronograph, but with a wider diameter and fluted lugs.
The model is illustrated in Patek Philippe Wristwatches by Martin Huber & Alan Banbery, first edition p. 231 pl. 386, second edition p. 303 pl. 459 and in Armbanduhren - 100 Jahre Entwicklungsgeschichte by Kahlert, Mühe, Brunner, second edition p. 127.