Among 38 known examples of ref. 1436 in yellow gold with silver dials, thirteen have applied gold Breguet numerals, nine have applied Arabic 12 and 6 with applied short ?bâton? indexes, seven have applied long bâton indexes with double index for 12, four have applied Roman XII and VI with applied long ?bâton? indexes, three have applied Arabic 12 and 6 with long applied ?bâton? indexes. Only two of them have vertical subsidiary seconds and 30-minute register dials, making them particularly rare. Patek Philippe split-seconds wrist-chronographs date back to 1923. No. 124824 was originally sold on October 13, 1923 (see the Antiquorum sale of November 1999, lot 448). These extremely rare watches are highly important collector's items. Between 1938 and 1971 the majority of them were cased with reference 1436, which was preceded by the legendary ref.130. The Split-Seconds Chronograph was designed to time two events which begin simultaneously but conclude at different times, as well as a single event for which an intermediate timing is necessary, such as horse or car races. Patek Philippe was one of the first to introduce modern split-seconds chronographs,-as early as 1862. (No. 17557, see Antiquorum, October 18, 1992, lot 590.) The split-seconds mechanism employs two central chronograph hands. Both hands are started at the same time. The split-seconds hand can be stopped while the chronograph hand continues to move. The split-seconds hand can be reunited with the chronograph hand in order to time another event. This complication is especially useful during sporting events such as a horse race, a car race or a ski race.