Calibre 13ZN

Notes

The 13ZN began development in 1935 at the behest of the technical department who wanted to replace the aging and expensive to produce 13.33Z. It was made in both a monopusher and, now standard, two pusher design. A chronometer version without chronograph function was made for the Chronometer trials. A central minutes version with a 12 hour counter was also developed during World War II. Though the calibre was originally intended to reduce the cost of producing a wrist chronograph movement for the Longines factory, by 1944, the technical department was again instigating for a less expensive and easier to produce movement that would allow them to keep up with the incredible wartime demand for chronographs.