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Joël Pynson and Sébastien Chaulmontet
First published: September 2016
Updated: March 2026
There is one small detail that sets these chronographs apart: the bezel, which is discreet—as it generally protrudes only slightly from the case—features a knurled edge to make it easier to grip and adjust.
These calibers are sometimes referred to as the “Landeron 185” [1]. The problem is that the Landeron 185 itself is equipped with conventional pushers. An analysis of period documentation is therefore necessary to characterize these attractive chronographs more precisely.
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, most notably, the Tri-Compax in 1943. These companies were manufacturers and therefore did not rely on Ebauches SA for their movements.
Given the success of these chronographs, it’s easy to imagine that the “établisseurs"—a term used to describe companies like Breitling, Heuer, Doxa, Le Phare, Léonidas, Record, and many others, which did not manufacture their own movements—must have put pressure on Ebauches SA to obtain chronograph-calendar calibers. The response was slow but substantial. The first chronograph-calendar caliber offered by Ebauches SA was the Valjoux 72C in 1946, followed by the 88 the following year. But as early as 1948, the trust’s two other chronograph movement manufacturers, Venus and Landeron, introduced no fewer than 13 new calendar calibers, with 10 more in 1950 [2]! A wide variety of combinations were available: date, day, month, moon phases, date via a central hand, date via a hand at 12 o’clock or 6 o’clock…
At Vénus, customers could even request an additional split-seconds hand, and at Landeron, an innovative way to adjust the calendar functions: a mechanism controlled by a rotating bezel, which eliminated the unsightly small pushers around the edge of the case.
Five Landeron calibers are equipped with this rotating bezel adjustment: the 58 and 59, launched in 1948, and the 10, 56, and 57, launched in 1950.
Calibre Landeron 57
The common features of these calibers are as follows: a date hand at 6 o'clock, and a day and month display at 12 o'clock. None of these calibers features a moon phase display or a split-seconds chronograph.
Calibre Landeron 56
Calibers 58 and 59 have a diameter of 13¾ lines, or 31 mm; calibers 56 and 57 measure 14 lines, or 31.8 mm; and finally, caliber 10 is smaller (13 lines, or 29.25 mm), and, most importantly, it is the only one equipped with a column wheel.
Calibre Landeron 10
What really sets them apart is the base movement on which the calendar mechanism—with its unique adjustment—is mounted:
- 58: Landeron 48 base movement without a column wheel
- 59: Landeron 51 base caliber without column wheel
- 10: Landeron 11 base caliber with column wheel
- 56: Landeron 54 base caliber without column wheel
- 57: Landeron 55 base caliber without column wheel
A view of the calendar mechanism beneath the dial shows how the pushers (left diagram) and the rotating bezel (right diagram) work. On the left, the correctors move the date, day, and month wheels by translation. On the right, the correctors have a rotation axis and are driven by the bezel when it is rotated.
Production of these calibers was very short-lived: about five years. Ebauches SA announced in 1955 that they were no longer being manufactured [3]. As a result, chronographs equipped with them are quite rare, and few companies actually used them: Boma and Titus are two examples. Boma was the brand of the Georges Weill factory in La Chaux-de-Fonds. Titus was the second brand of Solvil, a company that had taken over the operations of the famous chronometer manufacturer Paul Ditisheim in the 1920s. They can also be found with unmarked dials, or bearing the generic term “Swiss Chronograph.”
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 movements were not intended for high-end watches; they are often found in gold-plated, non-waterproof chronographs with dials that have often aged poorly. One must also be wary of haphazard assemblies and remember, for example, that the presence of a moon phase complication is highly suspicious. If one were to single out just one movement from this series of calibers, it would of course be the Landeron 10 with its column wheel. But it is a rare bird…
[1] For 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} See the catalogs published by Ébauches SA in 1949 and 1950
[3] Ébauches SA Catalog, 1955
Notes:
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