The CD-35z was the base model.  I got mine new in 2001.    There was then the CD-40z and then the CD-45z.  The lower 2 models dont have CD changer control facilities, whereas the 45 does.
Cant remember the other details.  CD-400 is the current base unit, probably on a par with the 45.
Just out of interest mate, what did you pay for it?