Yup...I've seen plenty of Zeniths (i386 & i486 models) in Faraday cages.
For that matter, I've seen a bunch of MacIIfx decked out similarly. Tempest
rated boxes. My first job was with a shop (SecureWare) that did high
security versions of Unix for these things. SCO-based for the Zeniths &
A/UX-based for the Macs. The Unix was refered to as CMW (Compartmented Mode
Workstation), was validated as a B1-level system (in Orange Book speak), and
featured a secure window manager based on X (windows have security labels,
and you couldn't do things like cut and paste between windows with different
security labels). Pretty kewl, if you are into that sort of thing.
Ken