Im calling BS... custom computer, custom OS...i dont think so... maybe obscure or arcane......also 5.25 inch floppys first came out in 1976....before that you had 8 inch floppys
I started as a tech in 1980 as worked on stuff that would be “old” even back then...
We had at work back then, 79-80, PDP-11’s that used 8 inch floppies!..................
The first Apple 1 came out in 1976 for $666
So an Apple ( what Satan tempted Eve in the garden)...for 666?( the number of the beast)....
Gee did we miss it...Steve Jobs was the Antichrist?...it explains the cult of Mac ;)