Re: Time machine
In 1990, my money would be on either IPX/SPX or NetBIOS Frames (NetBEUI).
If the office had a Novell Netware server doing file/print, then the former. If they had OS/2 doing that for them, then the latter. Not that this will be news to anyone who was there at the time, mind!
I started my first job in 1995, and never saw a Banyan Vines network - although I often saw it in documentation as supported by products.
After a bit of research I've found that 3COM had an old network protocol called 3+ that was based on XNS, but by the time of this story they'd thrown that out and joined Microsoft on the LAN Manager NetBIOS and IPX/SPX train. By the time I started work, 3COM was mostly associated with the hardware layer - network cards, hubs, and those newfangled switches...