Roger, back in my day there was no such thing as a color enlarger or even an enlarger with filter drawers.

Drew, There were several iterations of Ilfochrome paper and chemistry as they moved from one bleach to another. They went from H2SO4 to Sulfamic acid and changed the type of catalyst. We followed this closely at EK. You might not see the changes, but they were there even if minor. Even the dyes were changed slightly.

PE