Hi Dave
Over the years we have seen a variety of details associated with the so called Monnin Diver. The one with all the trade mark signs has the "Made in France" on the dial, Cathedral hands and G Monnin signed movement and case back. see here: http://classicheuers.blogspot.co.uk/2009/01/heuer-844-french-made-diver.html
Then we get the rest which have a combination of some of these elements. The common thread is the dial with distinctive red 13 to 24 numerals and the 844 stamp on the outside of the case back. I am having trouble posting pictures so here is a link to one I had that was similar to yours: http://www.heuerworld.com/photo_5636452.html
One could surmise that as production moved from G Monnin in France to Heuer in Switzerland the dial changed and the Made in France was dropped but not replaced as some components may still have come from France. Later versions with the standard dial (no red numerals) had Swiss Made on the dial. This therefore could be a transitional dial.
Hope that helps.
regards
Paul
www.heuerworld.com