https://www.watch-wiki.net/doku.php?id=lemania_2310

In the 1940's, Lemania and Omega worked together on a project called “27 CHRO C12” to develop a 27 mm diameter chronograph with a 12-hour register. Lead by Albert Piguet and Jaques Reymond, this project resulted in the 1942 launch of the Lemania 2310, called Calibre 321 by Omega.

Cal. 2310 was a column wheel design with a screwed balance oscillating at 18,000 A/h. It has a distinctive “wishbone” shaped bridge that makes it recognizable to many.

This movement was famously used in the Omega Speedmaster from 1957 through 1965 as well as the Omega Speedmaster Professional from 1965 through 1968, where it gained fame as the “moon watch” movement. It was also used in the Omega DeVille, Omega Seamaster, and watches from Patek Philippe (as Cal. 2872).

The cam switching Lemania 1872 family replaced the 2310 for most applications beginning in 1968.