Great overview and wording Lou unsurprisingly, thank you !

Some more information about the Space the Space-Compax

In 1961 at the Basle fair, UG presented the Polerouter Sub

here's the most well known version

credit : Amanico - ThePurists

which will be followed by this one

credit : GVM

and this one

here's a period advertising

In 1968, UG decided to focus its expenses and technical efforts on innovations (ultra thin movement 2,5mm height, Unisonic movement developed with Bulova, ...),
this is why they decided to stop production of in-house calibers.

Late Tri-Compax are an exception since they were offered up to the early 70s powered by the 281 Cal., I believe they were many in stocks available at the time.

By 1965, UG started V72 powered chronos, like the famous Compax

By the end of the 60s, UG launched the Space Compax

here's the only known period advertising

The first killing feature of the Space-Compax are its rubber pushers

here a diagram drawed by an Italian collector showing details of the pusher mechanism

there's also a "big crown" with screwed pushers

Reading the advertising, we understand the Space-Compax is positioned as the Submariner version of the Compax
Thanks to these unusual pushers, screwed crown and pushers, the watch is advertised to dive up to 25 ATM.
The chrono complication associated to the bi-directional bezel allows decompression timings.

Another unusual feature of the Space Compax is its "double asymmetry"

of its case (40mm)

and also its pushers

like any V72 powered chrono

the crystal is domed

and signed

contrast between registers and dial is very nice

we also find some typical UG signs

Art Deco 12

blueish registers hands

The second hand counterweight is very long

H/M hands have a typical UG style shared by many other UG period production

a movement photo 85 signed

Case back is srewed, serial were very lightly engraved, they're often vanished

something strange for the Heuer collector is the Gay-Freres bracelet is amazingly light at wrist compared to what we use to wear

the clasp is different from those which go with the Compax and the Polerouters

end-links are signed UM

a (very nice) dial variation was available

Here John Bucknum, Chuck Maddox thought he was wearing a Space Compax

Here a Japanese period catalog showing the Polerouter Sub, the Space Compax and a late Tri-Compax among others

As Lou said, many frankens around with this rare and sought after chrono

we sometimes see squared edges cases

but I've never seen any UG catalog showing such a case type

At the end, very few information known for this watch, very few good /original samples on the market

and a highly appealing watch

which is always a joy at wrist

cheers,

Laurent