Many web sites nowadays claim that 4.2.10 was the last COHERENT version.
This is wrong, there was 4.2.12 and 4.2.14. I do not have 4.2.12 disks,
because back then I had all sources needed to build a 4.2.12 system from
a 4.2.10 distribution. Nowadays you can do that too with everything open
sourced.
In 4.2.14 there were so many changes that one really needs a complete
distribution. I found time to fiddle (don't ask) with 25 year old floppy disks and got
them imaged. The 4.2.14 distributions disks are available at:
https://www.autometer.de/unix4fun/coherent/ftp/distrib/Coherent-4.2.14/
I have installed the base system on Virtualbox and it's working stable and solid.
When I have spare time I'll also install the DDK and the 4.2.14 kernel sources
on the box, to see how and if the stuff works.
Anyway, you can install and examine the distribution your self :-)
Have fun,
Udo