Here we go, some images and provenance. Quite an interesting story.

I'll tell you the majority of what I know

The Watch

1940s Heuer one button chronograph.

Manual winding nickel lever movement, black dial, gilt Arabic numerals, engine-turned subsidiary dials for constant seconds and 30-minute register, polished case with snap-on back, with inscription (includes the date '1942' on the case-back) dial signed Heuer, case and movement signed Gubelin, 34mm diameter.

Some history

The watch belonged to Mario Mylius (1912-1980). He was from quite a prominent family in Basel, and rose to the rank of Colonel in the Swiss Army, and was a champion equestrian, winning countless prizes, over many decades. He was also responsible for purchasing and managing the horses for the military, (bought from Austria, Spain, Ireland and other sources).

Herr Mylius competed in the 1936 Berlin Olympics (on 16th August), where he represented Switzerland in the Individual Three Day Event (as a Lieutenant), and was the youngest competitor in the event. His horse at the time was called 'Saphir'.

Herr Mylius in action

and meeting Prince Philip at one of the Equestrian events

The 1942-inscribed Heuer was one of the many prizes Mario won in later life (as the inscription on the case-back attests; a show-jumping competition in Luzern, 1942).

The watch has remained within the family until the present day.

Mario wearing the watch in around 1973

Would be great to confirm the Heuer / Gübelin connection and share any other thoughts on the forum.

Regards

Thomas
www.heuerheritage.co.uk