http://en.wikipedia.org/wiki/Marshal...mber_confusion
It all went wrong from the beginning...for example they named a 4x10 30W combo
1961 (in 1965!)
The same model with 2x12s was named
1962. Marshall indeed got started in 1962 with a head known as JTM45 (2245), despite only having 30W and the 1962 was based upon that circuitry. In all the confusion, it was no wonder that people started calling the 1962 combo the "Bluesbreaker", after an album that made the sound famous:
That's also why people use (unofficial) terms like Plexi (1959) or Jubilee (2555), and why Marshall themselves have rationalised the terminology. Marshall are now also using the nicknames in the official designations, for example the reissue 1959 SLP 100W, stands for Super Lead Plexi. The 1962 is now officially the 1962 Bluesbreaker.
Ironically the album that made Clapton, the Bluesbreakers, the amp and arguably Marshall famous, was nicknamed after the comic book Eric can be seen reading, IE
the Beano album
IF I ever get a Marshall reissue it will be one of those.
although that 1974X is pretty cool as well, a Plexi reissue is tempting, even if you have to crank it up...