We received the tape in June 1974, due to delay in printing more documentation.
The documentation we received must have been for V4, since the label says to
“see manual for format”, written later by Jay Lepreau, the OS researcher in
whose documents it was found. Furthermore, the blue embossed label on the side
says UNIX V4 DIST, which I presume was put there by Bell Labs.
https://archive.org/details/thompson_to_newell_1974-05-31

UNIX wasn’t versioned as we know it today. In the early days, when you wanted to
cut a tape, you’d ask Ken if it was a good day—whether the system was relatively
bug-free—and copy off the research machine. The manuals were versioned and you
got whatever the last one was.

The V5 manual is dated June 1974 (anyone know a better date?), same as our tape.
I suspect the next manual was finished days or weeks after this was sent, so
this may perhaps be the most extreme drift in an extant copy of UNIX between the
manual features and the shipped features.

The Dennis_v5 distribution on TUHS is dated 21 March 1975, just two months away
from the May 1975 release of the V6 manual. (Which explains why I found it so
close to V6 when I studied it.) The Utah “V4” is a much cleaner V5 than the V5
we have. I’ve had been saying It’s probably V5 minus a tiny bit, which turned
out to be quite true.

Thalia