Talk:Mac OS 7.1

What does the "Z1-" mean in this system?
I have a PowerBook 170 that I acquired from my grandmother in 2014, and in the About This Macintosh dialog it reports the system software as "Z1–7.1". What exactly does the "Z1-" mean here? Edgar Searle (talk) 06:25, 9 August 2022 (UTC)