So this is pretty neat. From the code we can see that:

If you set the console switches of the PDP-11 to the magic number 173030 init executes "/bin/sh -" on the console tty (probably a decwriter).

Otherwise it starts /etc/getty on /dev/tty0 - tty8, ttya, and ttyb.

It also starts /etc/dpd ("Dpd is the 201 data phone daemon. It is designed to submit jobs to the Honeywell 6070 computer via the GRTS interface."), /usr/mel/da (???) and /usr/demo/dds (???).

When user logs out it's copying the utmp entry to wtmp.

I can see that the init binary is 456 bytes.

It's mounting hard drives /dev/rk1-rk3 on /usr, /sys and /crp. Maybe no /etc/fstab yet. I guess /dev/rk0 had root.