Excerpts from netbsd: 11-Dec-97 Re: Installing from FreeBSD? Ty
Sarna@endicor.com (706)

> Apparently (from past threadshere) OpenBSD uses a different id (166?)
> and falls back to 165 if it doesn't find a 166 (or whatever it was). It
> does this for the purpose of coexisting with the other BSDs better.
> 
> There was some talk of having NetBSD do the same thing, with a different
> id (167?). It seems like a good idea to me. Any chance this will happen
> (after 1.3, obviously)?

The idea didn't have many friends, and there is still the
problem that there is no authority which assigns the
IDs.
If a notion of disk slices is introduced one day, it could
be possible to have 2 partitions with the same id on a disk.
there is a number of technical problems, in particular for
the bootloader, but it can be done.

best regards
Matthias