But then there's this:
https://www.princeton.edu/ssp/joseph-henry-project/unix-and-c/bell_labs_136…
"C is also available on the HIS 6070 computer at Murray Hill, using a
compiler written by A. Snyder and currently maintained by S. C. Johnson.
A compiler for the IBM System/360/370 series is under construction."
Due to the description of the IBM compiler, it seems to predate the V6
revision.
Here's a revision from 1974:
https://9p.io/cm/cs/who/dmr/cman74.pdf
"The language is also available on the HIS 6000 and IBM S/370."
Does this imply the Princeton copy is from before 1974?
Also Appendix A from the K&R book has the text from the C Reference
Manual.