The PowerStack was one of the Motorola Computer Group’s entries into the personal computer (PC) market around the time the Microsoft Windows/Intel x86 juggernaut was stumbling with their mass market Windows 3.11 replacement. It’s a compact, modular, efficient platform featuring IBM/Motorola’s PowerPC CPUs as well as best-in-class contemporary interfaces like PCI and SCSI. A compute element could be stacked with other modular I/O and storage cases to expand its capabilities without having to rehome the computer in a larger chassis.
I had never heard of this machine before, illustrating just how much random non-x86 machines were produced in the ’90s. This one definitely looks more out there than most, and most likely utterly impossible to find anywhere.