These look similar to those watches that are known to have 'cylinder movemets' with 'cylinder escapements'.
According to Wesolowski, [2003] (p.92):
"cylinder escapements were not known for their accuracy, and had all but been superceded by the vastly superior lever escapement mechanisims by 1920"
However, the Helvetia, is very similar to that on the next page of ZW's aforementioned book, and an example was "reputedly found to have been worn by crewman of a Heinkel He111 bomber during the Battle of Britain"(p.93 ibid.)
Wesolowski also writes that "They were designed to be worn around the sleve of a flying suit and had broad lugs which allowed the fitting of a strong leather strap."(ibid.)
I am fond of the crown, as it is easily manipulated whilst with gloves on. Useful pointer, too, additionally, not having increments formally marked can be useful was a marker can be employed each time, or an organic material to make ad hoc markings each flight-but that's an idea.
Many be of interest. N.B. They do not all, when in such cases, have an 'infereior' cylinder escapement; that need be verified upon each watch.
Saw one similar on 'epray', but relented; not bidding, inspite of really liking the look/ease of use, but still fond of them.
Best Wishes,
Pottinger+ :)
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'A Concise Guide To Military Time Pieces 1880-1990'; Wesolowski, Z.;(2003);The Crowood Press. [ISBN:186126304X]