I used a DataDesk 101 on a Plus at work in the 1980s. It was not the same model as the one mentioned. It had the 128K keyboard connector only but was a full size keyboard with function keys. I *think* it was less bulky than the one in the link.

The keyboard shipped with some macro software (possibly Tempo?) which didn't work with System 6. Nor did MacroMaker in System 6 work with the keyboard. QuicKeys, however, was brilliant. I also managed to get some VT keyboard mapping to work in VersaTerm for Vax usage.

Somewhere in the stack of junk, I have a Dell keyboard that provides dual XT/AT functionality. It is quite a nice keyboard (the C key switch needs cleaning, which drives you insane when using DOS) but a manual switch needs to be moved to enable XT or AT functionality. I daresay that the DataDesk 101E requires the same.

If I spotted a DataDesk 101 for sale, I might be tempted.