Digital Equipment Corporation
VAXstation 3100 M76
This is a VAX workstation, running the VMS operating system, with Motif / XWindows graphics.
I spent many years working professionally with VAX systems that would fill half this room and cost $100K or more, even in 80's dollars. It was strange enough when they scaled them down to desktop size, and even stranger to have one here on my desk at home.
Of course the 486 I had 10 years ago would probably run rings around it speed-wise, but VMS was a cool OS.