The Marshall JCM 800 has grown onto one of the most desireable Marshall amps. It’s a little funny beause at one time guitarists did not really care for the master volume marshall amps.

The 2203 is the 100w version. The 50w is the 2204.

The JCM 800 was a direct descendant of the JMP series of amplifiers. In the picture below notice the horizontal jacks. Earlier 800’s had vertical jacks. There were some very minor circuit changes when they switched to horizontal jacks. Many consider the vertical jack model more desireable.