I think this particular model falls in right after the gen X models (the roman numeral ones), which was at the tail end them being made by/with Zed audio... but I could be wrong. It's been a while since I've looked into amps.
Nonetheless for $50, it should be a good buy (as long as it's in working order).
The seller says there are no problems with it. Should I open the cabinet and look inside before going thru with sale? Or just hook it up and slam it?