. . . for the US Army, Nicolas. There were a few purely civilian models (delineated by a 2179 reference number without a -x), but chances are almost certain any 2179 you find will have US military roots.
The distinction between those with a 'US Army' engraving and those without (like mine) might well be significant to a sophisticated collector, but any 2179-x had the potential to be a military-issue watch. The most likely explanation for the large number of non-engraved specimens would be cessation of hostilities before they could be issued to active personnel. The bulk were probably sold to peacetime US military personnel thru American PX venues, or as military surplus years after the war. I believe mine is an example of the latter.
Basically, any 2179 is worth collecting as it's only one of two vintage references designated by Omega as a chronometer without actually having a chronometer (rg) movement. There's a possibility the hairsprings of these movements were distinct from those issued on a standard 30T2SC, but I'd have to do some deep research to confirm that supposition.
Best,
Art