Calibre 21.29

Notes

The 21.29 was based on the Calibre 21.59 from 1888 and designed to be a chronometer competition calibre. In the early 1900s chronometry competitions and the prizes won in them by manufacturers were an important marketing tool for large producers like Longines and Omega. In the late 1920s early 1930s as methods of avigation (aerial navigation) were developed in the US and abroad, demand suddenly appeared for a portable navigation chronometer and Longines chose to modify this calibre to suit this purpose. They gave the newer versions of this movement a center second hand and eventually a hacking seconds by the 1940s to better fit the intended role as an instrument for naval and aerial navigation. The calibre has a regulation cam in a snail shape that allowed for fine tuning of the balance as well as a power reserve indicator. The siderograph version of this movement also had a double flyback seconds mechanism located on the dial side.