Revealing mistake: In the swamp during the movie, Frank comes up and talks to Igor, who is running the projector. Although there is a film running, there is no film on either the supply or take-up reels.
Factual error: In the beginning, Hawkeye says that the patient was full of shrapnel from a claymore. M*A*S*H was set in the early 50's, and the M18 Claymore was only in the development stages in 1952, and not accepted and battle used until Vietnam in 1961.
Answer: It is actually Cencompac for Central Command of the Pacific. It is like the headquarters for all military activity in the Pacific Region (Japan, Korea, Okinawa, etc. The newer version of that is United States Pacific Command (USPACOM).
EMTurbo
And the abbreviations were used mainly by the Navy. Especially CENCOMPAC.
Https://en.wikipedia.org/wiki/United_States_Indo-Pacific_Command.