Computer it ain't.

dumb terminal it is.

As far as I can tell this is a Altos 'model five' Dumb Terminal.

Haven't seen one of those for 17+ years.

I used to work for a company that imported & sold Altos equipment including these things.

It was a greenscreen/dumb terminal that could emulate a VT220 terminal (as well the Altos emulation which was similar to the VT220 emulation I recall).

This terminal would have been designed to be used on either the Altos 586 or 986 multi-user computers running Xenix (Microsofts 80's attempt to dominate the Unix market).
Altos computers were based on the 8086 processor and were common in the mid to late 1980's.