It is obvious by the layout that it is made for a DEC-compatible terminal of some sort. The layout is the same as
DEC LK201 and there were clones of DEC terminals made by many companies.
The uneven yellowing on the keys leads me to believe that it has been refurbished by swapping keycaps from different keyboards.
The legends tell me that it is likely that is was made by Key Tronic and has their
foam and foil switches.