Omega

. . . but there was another, ref 2384, with a similar dial but different case.

[ref 2179 top, 2384 bottom / photo courtesy Bill Sohne]

Both are considered to constitute the US Army's contract order of ten thousand 'chronometer' grade watches.  The cal 30T2SC movements fitted to both were not chronometer grade, but were reputedly adjusted to chronometer standards. 

The 'US Army' engravings for them were different.

 

[ref 2384 / photo courtesy Evan]

[ref 2179 / photo courtesy Evan]

Reference 2179 is more common, produced in six* batches: 2179, then 2179-2 thru 2179-6.  Only 2179-2 and 2179-3 references have the 'US Army' engraving.  The succeeding batches were either delivered under contract but sold at PX's after the war, or were sold independently to civilian agents.  The rarest iteration, ref 2179 without a batch number, was produced years before the contract with the American military was signed.  I've seen only a few of these, including one with a black dial. 

Best,

Art

* Ref 2384 was produced in only one run, to the best of my knowledge.

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