Omega Seamaster Chronograph ST 176.007 (Part 1)

This is the first in a series of blogs devoted to Omega’s Seamaster Chronograph ST 176.007. Considered a classic of the 1970s, the model  has too many interesting features to set out in a single post.  A good starting place is to consider the piece’s  remarkable movement. In future blogs I will discuss some of the different versions produced by Omega and will also describe my experience owning a set of ‘twins’ (see illustration, below).

At the heart of the ST 176.007 lies a modified Lémania 1340: a haute horlogerie movement with a distinguished pedigree. Launched in early 1971, the caliber is the first of Omega’s high-frequency, self-winding chronographs and represents the company’s response to the Breitling/Heuer caliber 11 (‘Chronomatic’)  and Zenith El Primero  movements – both released in 1969 . The 1340  was manufactured at Lémania under the direction of engineer Raoul Henri Erard and designer Alburt Piguet.  Their joint efforts produced a three register, cam-switch actuated chronograph movement. The 1340  has two sub-dials: an hour-totaliser at 6 o’clock and a running seconds register (essential on a true chronometer) at 9 o’clock. Visually and technically, the most striking features are the fly-back chrono sweep second hand and central 60 minute totaliser with  cross (coloured white, blue, orange, or black depending on the dial design). The latter is a daring alternative to a more conventional sub-dial arrangement.

Caliber 1340’s famous bi-directional Lémania ball-bearing mounted rotor was invented by Marius Meylan-Piguet.  Application of ball-bearings increased the efficiency of automatic watch-winding, reducing the amount of wrist time per day needed to keep a movement ticking. A 45-hour reserve also assists performance. Power for the chrono mechanism is supplied by the driving and coupling wheels. The position of the cam regulates the raising and lowering of the coupling wheel on to the centre second wheel. To disengage, the reset hammer returns the centre second wheel to the zero position. A coupling yoke attached to the cam links to the hour and minute registers. The movement features a straight-line lever escapement (so-called because the arbors of the balance, lever and escape-wheel are in alignment), a monometallic Glucydur balance wheel, Incabloc shock protection (with striking mauve cap jewels), a micrometric index regulator with fine regulation via an eccentric screw, and a self-compensating balance spring. The latter is an alloy of nickel, chromium, berrylium, titanium, aluminium, and iron best known by its trade-name ‘Nivarox’. Springs made of premium-quality Niravox reduce the impact of temperature change on accuracy to around 0.3 seconds per day per degree centigrade, freeing watch makers to deploy smooth monometallic balance wheels (in place of bimetallic ones) since there is less need to exploit the expansion coefficients of different metals in order to compensate for timing errors generated by the spring.

The principal modifications Omega made to the Lémania base movement to produce the caliber 1040 were the addition of 5  jewels to the original 17, introduction of a day/night indicator by arrow on a revolving disk built into the permanent seconds sub-dial,   inclusion of a quick-set date function, and a splendid rose copper finish in place of the ébouche’s plain grey. This highly reliable, durable, and superbly assembled 81-piece movement is an exemplar, cam-operated, automatic chronograph. Its direct drive chrono functions can withstand appreciable shocks without the central second hand stopping or significant loss of accuracy occurring.

Despite its high quality, the 1040 proved relatively short-lived since the movement proved expensive to manufacture at a time when the Swiss watch industry started to encounter serious financial difficulties. Production ceased after 1975 and from 1978 Omega switched to the caliber 1045, based on the Lémania 5100. There is some debate over the respective merits of the 1040 versus the 1045 within vintage watch circles. Caliber 1040 lacks a hacking feature and a day function. It is also rarer since only approximately 82,200 movements were produced by Lémania for Omega. Caliber 1045 utilised synthetic (delrin) parts for day/date wheels, the related cams, and rotor supports  – a  commercial decision which offends some purists. Pillar construction was used to pin the stamped bridges and other parts to the main plate. A Kif shock absorbing system was also employed in place of Incabloc. Caliber 1045 powers highly desirable models in the Omega Speedmaster range,  including the Mark IV and Mark V. In truth, both the 1040 and 1045 are exceptional and four decades on are still favoured by some watch makers. Currently, 5100s power Sinn, Tutima, and Fortis chronographs. Between 1984 and 1999, ownership of Lémania passed from Heuer to Breguet and finally the Swatch group. This led to a revival of the 1340 in an adapted form, including addition of a fly-back capability. The resulting Lémania 1350 can be found in Breguet’s two type XX chronographs: the Aéronavale and Transatlantique.


1040 serialIMG_20141116_142054554

Illustrations:  (Left) Caliber 1040 with original rotor and serial number – example found online. (Right) the twins – for discussion in follow-up posts.