Albert Piguet and the 1942 design
Lemania 2310 was designed in 1942 by Albert Piguet at Lemania, the chronograph specialist based in L'Orient (Vallée de Joux). The architecture is a manual-wind column-wheel chronograph at 18,000 vph (2.5 Hz) with horizontal coupling, two registers (small seconds at 9 and 30-minute counter at 3, with a 12-hour totaliser variant), and 27 mm diameter (12 lignes). The construction is unusually well-finished for a chronograph caliber and physically compact; combined with its excellent chronograph operation feel (clean pusher action, clean reset), the design became the basis for high-end chronographs across the Swiss industry for the next 60 years.
Lemania within the SSIH holding
Lemania was, throughout most of its history, part of the SSIH holding company (Société Suisse pour l'Industrie Horlogère) along with Omega and Tissot. This corporate kinship is why the same Lemania caliber appears under both Lemania and Omega designations across the post-war era. Lemania designed and produced the bare ébauches; Omega and other group brands finished and rebadged them under their own caliber numbers. After the 1985 Swatch Group consolidation, Lemania was acquired by Breguet, where it continued to produce calibers under the "Manufacture Lemania" name into the 21st century.
Becoming Omega Cal. 321
Omega rebadged the Lemania 2310 as Cal. 321 from 1946 and used it in the Speedmaster from 1957 to 1968; the Cal. 321 was the movement in all NASA-qualified Moonwatches including the ST 105.012 worn by Buzz Aldrin on Apollo 11. The Lemania-original 2310 and the Omega-rebadged 321 are mechanically identical; the differences are in finishing (Omega applied higher decoration), regulation (Omega was tighter), and rotor / oscillating weight (no, the 321 is hand-wound, no rotor at all). Both designations refer to the same Albert Piguet design.
Becoming Patek Philippe CH 27
Patek Philippe rebadged the same architecture as CH 27, the basis of the Calatrava chronograph references for over 50 years until the in-house Cal. CH 29 launched in 2009. The Patek CH 27 used the 2310 as its core architecture but with significantly more elaborate finishing: hand-bevelled bridges, Geneva stripes, polished column wheel, 21-jewel jewelling, and Patek's own regulation. The CH 27 was the engine inside iconic Patek chronographs including the ref. 1463, ref. 130, ref. 5070, ref. 5170, and many high-complication references.
Other brand uses
Vacheron Constantin, Roger Dubuis, and various smaller manufactures used the 2310 base into the 2010s. Roger Dubuis built complicated chronograph references (Hommage Chronograph, Hommage Quantième Annuel) on heavily-modified Lemania 2310 architecture. The 2310 is one of the most-licensed and most-rebadged chronograph movements in horological history, alongside the Valjoux 72 and the modern Valjoux 7750.
Modern status: still alive in the 321 reborn
When Omega revived the Cal. 321 as a faithful reproduction in 2019, they also revived the Lemania 2310 architecture by extension. Production happens at the dedicated Atelier 321 in Bienne; the movement is hand-finished in small batches and goes into selected high-end Speedmaster references (the Apollo 11 50th, the "Ed White" stainless steel Caliber 321, and the Canopus Gold versions). For practical purposes in 2026, "Lemania 2310" is the historical / Patek-equivalent name, "Omega Cal. 321" is the modern brand-marketed name, and the only place to buy a new one is inside an Omega Speedmaster Caliber 321 reference.
