I have a Coliseum 300 bass head, and I got a manual here, too. If there's a schematic in the manual, check the date on the schematic. Mine is an eighties model (black knobs, compression, biamp, contour button under the gain) which were made after the red knob Coliseums (which were the models John Entwistle used in the seventies). They're fantastic amps, the manual is a fun read.
If I may offer a piece of advice, keep a piece of foam, like foam rubber or Auralex or even a bunch of carpet samples- some sort of cushion- between the amp and cab because the vibrations from the cabinet will shake the amp silly over time and then you'll have to go in some day and resolder everything.