I think you’ll have more luck with this question at alt.guitar.amp There somebody will certainly be able to answer your question, although sometimes things can get a little bit harsh over there, but don’t let that scare you.
What I can tell you about the amp: generally Marshalls from that era are regarded of as good amps. Its only been in the last 10 years or so that people are not always satisfied with new Marshall amps
Good luck