This is a scanned copy of a document of which several copies are known to exist, but there is no known provenance. It looks to date from sometime in the mid-1940s. There is no known record of any C3s being produced for the Army. If you know of any such contract or examples of Army C3s, please contact me at the email link below.
It's possible this was printed by Argus in anticipation of a contract for C3s that never materialized. The C3 manual has no contract number, like you see in manuals for the Kodak 35 or Graflexes made for the Signal Corps. It also has the Argus corporate logo and references 'Argus Incorporated' (the name the company took in 1944), which doesn't really feel like 'official' military/government use standards.
In any case, here is the link to a pdf of the Army Service Manual