The DOS 2.10 disks - which by the way I purchased in Australia - arrived today, so I tried to convince my IBM 5150 to boot. Unfortunately it did not recognize the disk at first, and continued to jump to the built-in Basic interpreter. I had no possibility to check the disk on any other system. What to do next? I mean this thing doesn't even have a BIOS, it has... DIP switches on the motherboard! I should note that my IBM did not come with the two standard 5.25" floppy drives, but one floppy drive and one 10MB hard drive, so I figured there might be some misconfiguration. Luckily I still found documentation on the 5150 DIP switch settings, and after flipping one switch I was able to boot.
Current date is Tue 1-01-1980
Enter new date:Current time is 0:00:12.89
Enter new time:The IBM Personal Computer DOS Version 2.10
(C)Copyright IBM Corp 1981, 1982, 1983
Next steps: Backup the only DOS 2.10 disk I have, and try to install DOS on the hard disk. Hard disks were supported from DOS 2.0 on - so this should work as well. Oh yeah, DOS 2.0 also introduced subdirectories...