Just letting anyone here might be interested knowing:

I've recently added the first released versions of DOS to my DBDOS
tool, this boots real DOS images, so you can experience what it was
actually like to run them:

I'm currently including the following:

1Microsoft MS-DOS 2.11
2Microsoft MS-DOS 3.31
3Microsoft MS-DOS 4.00
4IBM dev. pre-release of DOS 1.00
5IBM PC-DOS 1.00
6IBM PC-DOS 1.10
7IBM PC-DOS 2.10
8IBM PC-DOS 3.00
9IBM PC-DOS 3.30
10IBM PC-DOS 7.1
11FreeDos 0.84
12Caldera OpenDOS 7.01
13Paragon Technology Systems PTS-DOS 6.51 (Russian)

These are the ones I've found so far which I believe to be available free.

I'll be happy to add others, but I don't really want to "fill it" with
DOSes that are currently available in bootable form from the vendors.

I've got a thread about DBDOS here: Re: DosBox BootfloppyDisk

** And yes, I do know that as it boots under DosBox - some might suggest
** this should be posted there - but this is more about early DOSes than
** how they are booted - I hope the admins will allow it here