Reference
The Lemania 2310: The Same Movement in a Patek and an Omega
One 1942 chronograph ébauche ended up under a Patek Philippe grand complication, a Vacheron Constantin perpetual calendar, and the watch worn on the Moon. Almost nobody outside watchmaking has heard of it.
Ask which movement connects a Patek Philippe split-seconds perpetual calendar, a Vacheron Constantin, and the Omega Speedmaster, and the honest answer is a company most people have never heard of.
Lemania made ébauches — unfinished movements sold to maisons that finish, decorate and rename them. Its calibre 2310, designed in 1942, is arguably the finest chronograph base ever produced. Six calibers in this library are built on it.
Where it came from
In the early 1940s Omega and Lemania set out to design a compact chronograph for wristwatches rather than a shrunken pocket-watch movement. Albert-Gustave Piguet, Lemania's technical director, led it. The result was a 27 mm column-wheel chronograph with a horizontal clutch, and it was good enough that it outlived everyone involved.
Omega took it as the calibre 321. Lemania kept selling the same base to anyone who could finish it to their own standard — which turned out to be a short list.
Column wheel and horizontal clutch
Two design choices explain why maisons kept buying it fifty years later.
The column wheel is a small castellated wheel that rotates a step with each press, its columns raising and lowering the levers. It is expensive to make and demands precise finishing, and it gives the crisp, mechanical click that a cam-switched chronograph does not. It is the difference you feel in the pusher.
The horizontal clutch engages the chronograph by sliding one wheel into mesh with another. It is visible through a display back — the moment of engagement is the most satisfying thing in mechanical watchmaking to watch. Its drawback is a slight stutter of the chronograph hand at start-up, as teeth find each other. Modern vertical clutches remove the stutter and remove the spectacle with it.
Neither choice is the efficient one. Both are why the 2310 is prized.
Who used it, and for what
| Caliber | Maison | Built on it | Watches |
|---|---|---|---|
| CHR 27-70 Q | Patek Philippe | split-seconds + perpetual calendar | 16 |
| CH 27-70 | Patek Philippe | chronograph | 9 |
| 1142 | Vacheron Constantin | chronograph | 6 |
| 1141 | Vacheron Constantin | chronograph | 3 |
| 1141 QP | Vacheron Constantin | perpetual calendar | 3 |
| 321 | Omega | chronograph | 2 |
Thirty-nine watches in total — the smallest ébauche family in this library, and by some distance the most exalted.
What Patek did with it
The CHR 27-70 Q is the extreme case. Patek took the 2310, added split-seconds works and a perpetual calendar, and finished all 407 parts in-house. CHR marks the rattrapante, Q the quantième perpétuel.
A split-seconds chronograph carries two superimposed central hands. Press the third pusher and one stops while the other runs; press again and the stopped hand flies forward to catch up. Doing that without disturbing the rate of the movement is one of the genuinely hard problems in watchmaking, which is why Patek could assemble only about a dozen reference 5004s a year.
The plain CH 27-70 is the same base without the split-seconds — the movement behind the reference 3970 and 5070.
The Omega side
Omega's 321 ran the Speedmaster from the CK2915 of 1957 until 1968, when the cheaper cam-switched 861 replaced it. That window includes 1969, so the chronograph that went to the Moon was a 321 — a movement whose base was also, at that moment, sitting under Patek Philippe grand complications.
In 2019 Omega put it back into production. The reissue is assembled in a dedicated atelier in Bienne at a rate of one to two thousand a year — small enough that it functions as a separate collection rather than a variant.
What happened to Lemania
The company that made all of this no longer exists under its own name. Lemania became Nouvelle Lemania, was acquired in 1981 by the group that would become the Swatch Group, and was folded into Breguet in 1999. The 2310 survives inside Breguet as the calibre 533.
That is the quiet ending to the story: the ébauche that Patek Philippe, Vacheron Constantin and Omega all chose is now the property of a single group, and no longer for sale to anyone outside it. When Patek needed a chronograph after that door closed, it had to design one — the CH 29-535 of 2009, its first in-house manual chronograph in decades.
Read that way, the in-house movement era was not purely a marketing turn. It was partly what happens when the suppliers stop being independent.
The point
The 2310 is the clearest argument against judging a watch by whether its movement is "in-house". A bought-in ébauche, finished to Patek's standard and loaded with a perpetual calendar, is not a compromise — it is a base so good that the most demanding maison in Geneva chose it over designing its own.
What separated those six calibers was never the architecture. It was the finishing, the complications built on top, and the standard each maison held itself to. That is usually what separates watches, and the 2310 makes it unusually easy to see, because the variable underneath is held constant.
All six caliber pages list the watches here that run them.