SSK: Space Saving Keyboard, would be referred to as a "tenkeyless" these days since it lacks the numpad but has everything else as usual.
Industrial: IBM buckling spring keyboards sold with some industrial equipment. Their main peculiarity is a gray, instead of beige case. Special, color-coded, purpose made keys are common on them as well.
Industrial SSK: combination of the above, rare, sought after, and has reached stratospheric prices in auction before.