and I can no more summarize UG in one post than you could Heuer...but I'll start if other enthusiasts chime in.

It's a vast topic because UG was a multifaceted company with many achievements to its credit. From the 1920s to the 1960s it was perhaps the premier house for complicated chronographs, and one of the two or three most respected chronograph manufactures. Late in that period it introduced its micro-rotor automatic movements and the Polerouter line which became another great pillar of the manufacture.

Since we are where we are, let's stick to the chronographs. UG claims to have introduced the worlds first wristwatch chronograph in 1917, the world's first wristwatch chronograph with two pushers in 1932, and the world's first chronograph with three counters in 1933. They based their chronographs on a series of in house movements (in fact supplied by Martel under exclusive contract) that were more or less scaled versions of the same basic ebauche. The model lineup was dynamic, but in their period of greatest glory - say 1940 to the 1960s - it ran as follows:

Uni-Compax: two-register chronograph
Compax: three register chronograph
Aero-Compax: three register chronograph with a fourth "reminder" subdial consisting of a twelve hour clock face set from a left sided crown
Dato-Compax: three register chronograph plus fourth subdial with pointer date
Tri-Compax: three register chronograph with date, day-month and moonphase.

The Compax you show in your post is actually a late model, driven by a Valjoux 72. Why? Because Martel had been acquired by Zenith in 1960, and Zenith cut off the supply of chrono movements to UG. Incidentally, in buying Martel, Zenith also acquired the expertise that gave birth to El Primero nine years later. That's a separate story, but the interrelationships of these legendary companies are interesting to me and explain how Zenith, historically NOT a chronograph house, could have produced one of the greatest chronograph movements ever.

Below, I have reproduced a post on the Tri-Compax I made in another forum - pardon the redundancies. All you UG enthusiasts chime in!

The Tri-Compax is a wristwatch with three complications - chronograph, complete calendar and moonphase - hence the name. It is a common and widely held misconception that Tri-Compax refers to the three dial layout on many chronographs. The irony of course is that the real Tri-Compax has four subdials. For UG, a three dial chronograph, because it only had the chronograph complication, was simply a 'Compax.'

The Tri-Compax was UG's most complicated chronograph and flagship model, introduced at the Basel watch fair in 1944 for the company's 50th anniversary. It remained so into the 1970s, when UG hit rocky times as did every other manufacture with the advent of quartz. An additional short run was produced in the mid 1980s with leftover ebauches. It is powered by one of UG's two core engines, the cal. 281, an in house caliber developed under the direction of CEO Raoul Perret, the son of the original founder.

The Tri-Compax exists in dozens of versions. UG reserved 100 numbers to code the different models, and ended up having to add suffixes to describe sub-variations, just to give you an idea of the variety.

So for your consideration, my two examples, both late versions with waterproof pushers and twisted lug cases. Although there is a design similarity with teh Speedmaster cases, these are smaller at 35mm

ref. 222100-1, produced in 1960 according to the serial number

ref. 881101/02, produced in 1966. The pulsometer bezel is as unusual for a UG as it is for a Speedmaster

Thanks for reading this far!