Hi Paul.

Welcome to the forum. I recognised the poster name from my time spent lurking on MWR, so good to see you posting over on here too.

The serial number of that example is neatly bracketed by two shown in sales material from 1938 over on OnTheDash http://www.onthedash.com/Guide/_Catalogs/1938_Catalog/

Those have 135402 and 155171 (though the latter could conceivably be a movement designation rather than a serial), but, given the size, dial configuration and pusher of your example I would agree that it probably predates that brochure. Interesting that Stewart's post turns up a similar, coin-milled case with single pusher from the 1950s though. Certainly Heuer had long ceased to offer Flieger type watches by then, maybe Leonidas was picking up some of that slack.

I've never really paid too much attention to Leonidas pre the merger with Heuer I'm afraid, so no real concrete information to add. I do have to say I'm impressed by how persistent they were with that Stefanovitch stamp though! Often we see just stamped casebacks or maybe a small dial change but to have that mark on dial, caseback and movement is certainly exhaustive!

Mark