Hagen here is the C3 ration in Korea.
All of these rations received their C 3, 4 etc designation before the Korean war. Certainly before 1949. 1948 seems to have been a very big year for deciding ration designations, stopping rations like the 10 in 1 and E ration, while the amazing K ration was declared "obsolete" also. Any changes in composition were just given a higher number. C 3 through to C7 were all being used concurrently in Korea!
C 3 A canned accessory item
1 12oz tin of fruit.
C 4 had a foil accessory packet, and 2 6oz tins of fruit. And a spoon! C3 had no bloody spoon! Can you believe that?
C 5 had 1 8oz can of fruit. Foil a/p, spoon.
C 6 changed the fruit composition again with 2 4oz fruit. foil a/p, spoon.
M and B units throughout seem to have been essentially unchanged. There was a change to the "recipe" of chicken stew between C4 and 5 which greatly increased acceptance of that product. Col Dobson of the QM branch mentions this in his 1951 report from the Korean theatre, and the great (and unexpected) unpopularity of the 5 in 1, due to the overprocessed texture of the meat items, and the impossibility of lightly equipped men preparing it, without limited cooking facilities.
Theres an obsession with tinned fruit here.. Col Dobson of the QM branch reported in 1951 that fist fights were breaking out in squads due to the uneven allocation of fruit with the C3, so this must have been an attempt to rectify this potentially serious morale issue.
Treesuit, the winter supplimental allocation of rations in the Korean winter was issued at the B ration level. There was no winter or cold weather C/RCI ration as such on issue, and none of the RCI/C series was specifically designed for Korea it seems.
Extra rations of high carb stuff like bread, cereals, instant mash etc were allocated to the cookhouses, giving an extra 500 -600 cals a day to the troops.