Browsing the back pages of Motor Sport magazine I came across this advert

and in a blow-up


Could it be that the contrasting sub-dials really were some sort of airline requirement, or was this just advertising fluff?

 

That's interesting, not sure - though if we look back at early pilot chronographs like the Breitling Chronomat and Navitimer, and even at the design of the original Autavia, they all do have contrasting subdials. So maybe that was the preference at the time, though if it were actually a requirement of the airlines we'd have probably heard of it by now!