kumpel, das 2121 wurde von ap, pp, vc und jlc zusammen entwickelt, jlc hat dann das werk hergestellt und jede der oben genannten firmen haben es auf ihre art nochmal bearbeitet. patek hat dann in den 80ern ein eigenes werk in die nautilus gebaut, ap, das 40% von jaeger hält, hat im jahre 2000 die gesamten fertigungsmaschinen von jlc gekauft und stellt das werk heute solitär her.

aber besser als thomas mao kann man es nicht sagen:




cal. 2120: c. 1967 - 1993
cal. 2121: c. 1970 - present

Calibre 2120: Ultra-thin automatic


height: 2.45mm (3.05mm with date, cal. 2121)

diameter: 28.00mm

Jewels: 36

19,800vph

hour and minute only, no date or seconds


The cal. 2121 variant with date, but still no seconds, was used in the legendary Royal Oak when it was shown in 1972.

There has never been a 2120 based movement with seconds (indeed, such is a near impossibility because of the inherent movement design - M.W. 0802)

cal. 2122 is actually part of the 2124/2125 movement family, rather than the cal. 2120 family.

Features: announced in 1967 as the thinnest ever full rotor auto movement, at 2.45mm, its 21 kt rotor is mounted on beryllium-bronze rails that rested on ruby rollers near the outer edge of movement, rather than on center bearings, allowing for less point friction and lower overall height.

The keyless works is designed so that when the movement is manually wound, the automatic winding parts are disengaged, thereby eliminating the chances of increased wear when an automatic movement is manually wound. Automatic winding is bi-directional, actuated by a rocker switch to engage one or another transfer wheel, depending on the motion direction of the winding rotor.

Designed to use the Gyromax-type adjustable mass balance, and along with the unique rotor rail and ruby runner support, the cal. 2120 is renowned for holding adjustment and regulation very well, as well as being a surprisingly robust and reliable calibre, considering how thin it is. Note, however, that not all cal. 2120/2121 implementations used adjustable mass balances, even within the Jumbo Royal Oak model lines.

There have been numerous questions about wear on the center axle because the winding rotor does not use ball bearings, or possible pre-mature wear due to the flying barrel design; that is, the barrel is supported only on one side. While aesthetically beautiful, there are concerns that this would lead to vulnerability to excessive wear.

I have spoken to a number of watchmakers with substantial hands on experience with older caliber 2120/2121, both in the factory and independent, and all have told me neither concerns are particular problems in reality.

The fear of axle wear is due to a mis-understanding or lack of understanding about the design of the winding system of the caliber, and the concerns about wear due to the flying barrel (affixed and supported only on one side) is more theoretical than real. However, aligment and proper set up of the barrel and bridge is absolutely critical, so properly trained servicing is a must. Patek, for their version of the movement, even went so far as to design and produce a custom tool specifically for this purpose.

One generally unexpected side effect of the ruby runner design, though - the winding action of the rotor on the ruby runners give an unusual winding sound, different than just about any other automatic winding movement on the market. I liken it to dry metal grating against metal, or the wheels on an old pair of inexpensive roller skates. This doesn't bother most proud owners of a cal. 2120 powered ultra-thin, but for new owners who may not have ever heard one previously, it can be disconcerting and erroneously lead them to think something is wrong.

Comments: The development of the calibre 2120 was jointly funded by the Big Three - AP, PP, and VC, the bulk of the development and production done by JLC, with technical assistance from AP. Original JLC calibre reference was JLC cal. 920; VC implementation cal. 1120.

The actual design conceptualization was done by a Belgian watchmaker working for JLC (PhD 02)

Because PP participated the least, financially, in this development syndication, they were not able to use the thinnest iteration of the movement, which only AP and VC (cal. 1120) used. The PP version of this movement, PP cal. 28-255 (cal. 28-255C with date) was 2.55mm/3.15 mm respectively, thus .1mm thicker in the equivalent version than the AP or VC implementation.

The cal. 2120 is widely considered a landmark movement, and still regarded as one of the greatest movements ever made. (MW GV PhD 02)

Until the sale of JLC to Richemont, JLC continued to produce the cal. 2120 exclusively for the use of VC and AP (delivered to AP primarily as a parts kit and unfinished ebauche) When JLC became part of Richemont, AP acquired the tooling and sole rights to produce the caliber as part of the sale of their 40% interest in JLC.

The tooling and production of the cal. 2120 movement family has now been shifted to Renaud and Papi in Le Locle, and now will be exclusive to AP. Other manufacturers, including VC, will continue to produce the movement (VC cal. 1120) until their present stock of parts is consumed.

(November 3 2003 update: VC has recently used up their very last stock ebauche. VC/YB 100303)

The calibre 2120 and variants power the major automatic big complications from AP, serving as a reliable and sophisticated automatic base movement.