[old_tv_nut]

Something to take note of: the Viewmaster 3D transparencies were Kodachrome dupes, and even the early ones did not fade. Not sure if there might have been a later period when they would have, or if manufacture was curtailed during the same time (WWII). So, this fading Kodachrome may be a case of a period when development chemistry was being modified, was still compatible with the same version of the film, but resulted in dies that were less stable for a particular version of the chemistry.

Viewmaster much later went to Ektachrome or other similar processes (especially as it was used more and more as a cartoon toy rather than travel pictures), and did suffer from pink fading.

Jack Coote, in The Illustrated History of Color Photography, mentions that Kodachrome II (process K12) introduced in 1961, had improved sharpness, grain, and permanence; but he doesn't say anything about variations in the earlier process after 1938.

He also says that the Kodachrome print processes were:
Minicolor: 2 1/4 x 3 1/4 or 5 x 7 1/2;
Kotavachrome: any size from 8x10 to 30x40, and used a contrast mask to improve image quality.

He says that these prints were not made after 1946, but similar prints dubbed Kodachrome Prints were made until 1955.