With Longines Extract from the Archives confirming production of the present watch in stainless steel and with calibre 13ZN, and its subsequent invoicing to Longines-Wittnauer, their agent for the USA at the time, on 7 June 1948.
Made in-house from 1936, the Longines caliber 13 ZN was the first ever chronograph made with flyback function and has become one of the brand's most sought after calibers amongst collectors. Considering the close involvement of Longines in the production of aviation timepieces, such a watch was a natural progression. Its pupose is to allow resetting of the chronograph while in operation in situations like flying where speed of reset is of the essence. In a standard chronograph the hand must be started, stopped and reset by separate actions.