Cal. 13ZN is a column wheel chronograph movement from Longines. Produced from 1936 through 1951, it was one of the few chronograph movements produced by the Saint-Imier company. Cal. 13ZN was produced in monopusher and dual-pusher variants, and some feature flyback and central minute counters.
One of the most notable Longines watches to use Cal. 13ZN was the waterproof Ref. 4270. Known for its “mushroom” or “umbrella” pushers, it was produced in small numbers and has become quite collectible today.