They found 86-dos 0.1 and 0.34, holy fucking shit!
https://archive.org/details/86-dos-version-0.1-c-serial-11-original-disk
https://archive.org/details/86-dos-v-0.34-221-81-02-20
MS bought the code of this operating system to create MS-DOS.
Therefore this is the oldest version of dos ever and probably one of the first ever created.