By the way, 4006 in St. Louis has cab access (or at least had the last time I was there) even though 4012 doesn't, albeit several hundred miles west.
These two pics (taken 7/23/2001) don't show the cab interior, but they do highlight the steel stairways that are/were in place to access the cab, one on each side. The first one also includes me and my crew, back in the day:
She was in fairly good shape back then as well.
Ahh, to be about 20 years younger right now ...