I actually don't think any UNIX variant ever shipped as a commerical product. My gut feeling while working on the project was that it was perhaps a reference implementation, documenting proper z-machine behavior the various assembly versions needed to match. But that's a literal guess, TBH.

The list of known system codes (used as identification for packaging and so forth) can be seen here: http://pdd.if-legends.org/infocom/fact-sheet.txt