Clearly the brake levers are not original (they are aero type which is more mid 1980's) and I'm guessing that many of the other parts have been changed. The original gearing was probably half-step which would explain the close gears in the front, but you should have a freewheel with wider spacing in the back. I'd guess that originally the freewheel had a much larger largest cog, but when the Suntour RD was put on it couldn't handle such a large freewheel and hence a closer spaced freewheel was put on. Purely speculation here.