Because Project Earthsave is a multi-national project, U.N.C.L.E. has been charged with safeguarding the new combination each August. Agents act as couriers, each carrying only part of the combination.
Calvelli, the associate producer of the episode, apparently rewrote Ware's draft extensively. While this wasn't reflected in the TV writing credit, it seems to have played a factor in the writing credit for the movie.