Longines Twenty-Four Hours

In the 1950’s Longines supplied watches to the Swiss national airline, Swissair. These timepieces, which had been developed specifically from the brand’s aviators’ watches, had a very distinctive 24-hour dial. This technical characteristic met the needs of navigators who, at the time, had to determine the position of the aircraft and set up a flight plan. Longines has now re-issued this watch for both historical and functional reasons, as well as for the aesthetic attraction it still holds. The new version has been given the name Longines Twenty-Four Hours.

In 2009, Harry Hofmann, a retired navigator from the old Swissair, visited the Longines Museum. He took advantage of this visit to present the company with a Longines watch that he used to wear when he was working for Swissair. This watch, with its 24-hour dial, is part of a series of timepieces produced by Longines in the 1950’s especially for Swissair navigators.

In mid-20th century aviation, one of the responsibilities of the navigator was to determine the aircraft’s position and to set up a flight plan. A reliable watch was therefore an essential part of his equipment. The fact that the flight crossed different time-zones in both directions and that the sun was not always visible as a point of reference necessitated instruments that could immediately indicate the correct part of the day. With a 24-hour dial navigators had no problem in this respect.

The watch that Harry Hofmann wore when he was a navigator for Swissair, flying DC-4s, DC-6s, DC-7s, DC-8s and Coronados up until 1974, had been specifically manufactured for the Swiss national airline by Longines in the early 1950’s; it bears the number 8237331. It is fitted with a Longines calibre 37.9N with a centre seconds hand, which had been designed in the 1940s and used in Longines watches intended for pilots. The back cover of the steel case of Mr Hofmann’s watch is engraved with the Swissair brand-name.

Longines’ archives reveal that it was one of a series of 70 pieces manufactured between 1953 and 1956 exclusively for the Swiss national airline. Technically, it is related to the aviator’s watch – the Longines Weems Second-Setting model, produced in 1927, or the Lindbergh Hour Angle watch made by Longines from 1932 on. The Swiss watch manufacturer has chosen this watch as a re-issue for both historical and functional reasons, as well as for the aesthetic attraction it still holds. It has been given the name Longines Twenty-Four Hours.

The Longines Twenty-Four Hours is fitted with calibre L704.2, a self-winding movement whereby the hands make one full circle of the dial in 24 hours. The stainless steel case has a diameter of 47.50 mm; the dial is matt black with 24 white Arabic numerals coated with Super-Luminova and has a railway-track minute circle. The time is indicated by hands coated with Super-Luminova and the watch has a centre seconds hand, all for ease of use, like the original model. There is a date aperture at 3 o’clock.

A sapphire glass covers the dial and this timepiece also has a transparent caseback, with its own cover, which reveals the delicate details of the movement. The inside surface of the cover is engraved with the words “Re-edition of a Longines navigation watch exclusively made for Swissair navigators, 1953-1956“ plus the watch number. The Longines Twenty-Four Hours is mounted on a black alligator strap and is water-resistant to 3 bar (30 metres).

Technical details
Reference number:Longines Twenty-Four Hours – L2.751.4.53.x

Movement
Self-winding mechanical movement
Calibre L704.2 (ETA A07 171)
16½ lines, 24 jewels, 28,800 vibrations per hour
48-hour power reserve

Functions
Hours, minutes, seconds, date, 24-hour circle on dial

Case
Circular, stainless steel, Ø 47.50 mm
Engraved and numbered back cover (unlimited series) on top of a sapphire glass
Water-resistance:3 bars (30 metres)
Glass:Sapphire with non-reflecting coating

Dial
Matt black
24 white Arabic numerals with Super-LumiNova
Railway track minute circle
Date aperture at 3 o’clock

Hands
Skeleton pear steel hour-hand with Super-LumiNova
Skeleton leaf minute-hand with Super-LumiNova
Stick with drop counterweight seconds hand

Strap
Black alligator with buckle

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