PP 12-600 AT
This was the first automatic movement produced by Patek Philippe's and one of the first such movements in history.
Calibre 12-600 AT was introduced by Patek Philippe in 1953 at the dawn of automatic movement technology. Although not the first automatic, or even the first with a central rotor setup, it appears quite modern apart from its use of small seconds. Today, Cal. 12-600 AT is considered one of the best movements in the history of watchmaking. About 7,100 Cal. 12-400 AT movements were made between 1953 and 1960, when PP 27-460 was introduced. That this replacement was closely related to Cal. 12-600 AT and remained in production until 1985 says much for the engineering behind this movement.
Patek was quite proud of this movement and wanted to differentiate it from the other automatic watches on the market, the majority of which used hammer movements. Therefore, they billed it as a “self-winding watch”, not an “automatic”.
As was typical at the time, the name of Cal. 12-600 AT explains its key features
- The movement was 12 ligne in diameter, or about 27 mm
- The movement was 6.00 mm thick
- The movement was automatic
The 30-jewel 12-600 AT features a solid 18 karat yellow gold rotor, consummately decorated with engine turning even though no watch at the time had an exhibition case back. Timing was kept using Patek Philippe's patented Gyromax balance wheel (introduced just two years earlier) and this wheel beats at 19,800 A/h. Aiding the Gyromax wheel is a swan neck regulator and self-compensating Breguet balance spring. The movement is adjusted to five positions, heat and cold, and isochronism. It is possible that some early examples lacked the Gyromax balance.
The design calls to mind Patek Philippe's mid-century hand-winding movements. Separate cocks are used for the balance wheel, escape wheel, and fourth wheel. A large bridge is used for the third wheel and center wheel and also acts as a mounting point for the rotor bearing. The movement is rhodium plated and finished to the standards of the Geneva Seal.
Cal. 12-600 AT is widely respected today but was not without issues. The massive gold rotor caused excessive wear on its bearing, forcing a mid-cycle redesign. The successor, Cal. 27-460 of 1960, includes a redesigned bearing. Additionally, a third case screw was required to keep the movement in place in the case. Finally, swan neck regulator proved less than satisfactory, causing engineers to develop a novel adjustable balance spring stud carrier for the replacement.
Cal. 12-600 AT was quite special at the time, and Patek Philippe reserved it for their finest watches. Every reference fitted with this movement was cased in gold or platinum with the exception of Ref. 2588 which was made in steel. This rare combination makes this one of the most sought-after Patek Philippe watches.
- PP 27-460 the successor