Looking at the manual for the Kodak Tourist: http://www.cameramanuals.org/kodak_p...ak_tourist.pdf

Interpolating from the recommendations there, and using Sunny 16 as the standard, I read the sensitivities of Verichrome Pan, Plus-X and Kodacolor to be equivalent to the current ISO of 25, whereas Super XX sensitivity appears to have been equivalent to the current ISO of 50.

This is the same as Jason's initial observations.