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By Joel Pynson and Sebastien Chaulmontet
A detail sometimes helps to identify them: the discreet bezel, which generally protrudes only slightly from the case, has a notch on the periphery to facilitate gripping and adjustment. These calibers are sometimes referred to as “Landeron 185”[1]. Problem: the Landeron 185 is equipped with conventional pushers. An analysis of period documentation is therefore essential to characterize these pretty chronographs more accurately.
A few rare attempts were made in the 1930s, but it was in the early 1940s that the first chronographs with calendar functions appeared: Angélus and its Chronodato in 1942, Universal with the rare Dato-Compax in 1942 and above all the Tri-Compax in 1943. These companies were manufacturers and therefore not dependent on Ebauches SA for their movements.
Given the success of these chronographs, it's easy to imagine that the établisseurs - the name given to companies such as Breitling, Heuer, Doxa, Le Phare, Léonidas, Record and many others that didn't manufacture their own movements - must have put pressure on Ebauches SA to produce chronograph-calendar calibers. The response was late but massive.
The first chronograph-calendar caliber offered by Ebauches SA was the Valjoux 72C in 1946, followed by the 88 the year after. But by 1948, the trust's two other ebauches chronograph manufacturers, Vénus and Landeron, were offering no less than 13 new calibers with calendar, and 10 more in 1950 [2]!
Numerous combinations were available: date, day, month, moon phases, date by central hand, date by hand at noon or 6 o'clock... Vénus even offered an additional rattrapante, while Landeron offered an original way of setting calendar functions: a mechanism managed by a rotating bezel, which did away with the unsightly little pushers on the periphery of the case.
Avional Chronograph with date adjustable by rotating bezel Base caliber Landeron 56 with additional Index Mobile
5 Landeron calibres are equipped with this rotating bezel adjustment: the 58 and 59, launched in 1948, and the 10, 56 and 57, launched in 1950. These same calibers also existed in versions with conventional small push-piece correction. The common features of these calibres are: date hand at 6 o'clock, day and month aperture at 12 o'clock. None of these calibres is equipped with moon-phase or split-seconds functions.
Calibers 58 and 59 have a diameter of 13 ¾ lines, i.e. 31mm, 56 and 57 are 14 lines, i.e. 31.8mm, and finally, caliber 10 is smaller (13 lines, i.e. 29.25mm), and above all, it is the only one equipped with a column wheel.
Anonymous chronograph with date adjustable by rotating bezel Caliber Landeron 56
What really sets them apart is the basic caliber on which the calendar mechanism with its distinctive setting is placed:
- 58: Landeron 48 base calibre without column wheel
This calibre was slightly modified in 1950:
- 59: Landeron 51 base calibre without column wheel
This calibre was also modified in 1950:
- 10: Landeron 11 base calibre with column wheel
- 56: Landeron 54 base calibre without column wheel
- 57: Landeron 55 base calibre without column wheel
A view of the calendar mechanism below the dial shows how the pushers (left-hand diagram) and rotating bezel (right-hand diagram) work. On the left, the correctors translate the date, day and month stars. On the right, the correctors have a rotating axis and are driven by the rotating bezel.
Production of these calibers was very short: around 5 years. They were announced by Ebauches SA as no longer being manufactured in 1955 [3].
As a result, chronographs equipped with them are quite rare, and few companies used them: let's mention Boma and Titus. Boma was the trademark of the Georges Weill factory in La Chaux-de-Fonds. Titus was the second brand of Solvil, which in the 1920s took over the business of the famous chronometer manufacturer Paul Ditisheim. They can also be found with anonymous dials, or bearing the generic term “Chronographe Suisse”.
Generic Swiss chronograph with date adjustable by rotating bezel Calibre Landeron 57
The expert's opinion
These technically interesting chronographs are not easy to find, especially if you're looking for a piece in good condition. These calibers were not intended for high-priced watches, and are often found on gold-plated or chrome-plated chronographs that are not water-resistant, with dials that have often aged badly. Some solid gold pieces do exist, however.
We sometimes see versions with Index Mobile. For the most part, these are vintage watches to which the rattrapante function was subsequently added, mainly in the 90s. In the mid-90s, Dubey & Schaldenbrand also launched two Index-Mobile models based on the Landeron 56, one in steel limited to 100 pieces, the other in gold limited to 50 pieces.
If there's only one movement in this series, it's the Landeron 10 with its column wheel. But it's a rare bird...
Boma chronograph with date adjustable by rotating bezel
Caliber Landeron 10
[1] Par exemple : http://forum.chronomania.net/mix_entry.php?id=63630#p63630
https://chronographes.net/2016/02/16/titus-cal-landeron-185-tournez-lunette/
http://cda.chronomania.net/forum_entry.php?id=143282
[2] Voir les catalogues édités par Ebauches SA en 1949 et 1950
[3] Catalogue Ebauches SA 1955