I'm looking for info on the differences in model numbers. How does a 4001S differ from a 4001. A 4000 from the latter.
Basically, is there somewhere that I can explore the suble differences in the model numbering. Any help?

Soulpreacher,

The 4001 has a bound neck and body and shark-fin inlays, and from the late 60s had Rick-o-sound as standard. Most people would think of this a the standard Rickenbacker bass;

The 4001S was the export "no frills" model as played by Sir Paul and Chris Squire, with no body or neck binding and dot inlays, and only ever came with a single mono jack;

The 4000 was the first model bass Ric produced. It looks like a 4001S in terms of neck and body but only has the treble pickup (and hence just two control knobs). In the 70s the 4000 went from through-neck to set-neck construction. A number of 4000s were routed for a neck pickup and sold as 4001Ss in the late 70s/early 80s.
The 4003 and 4003S are basically the same as 4001 and 4001s but with a revised (and improved) truss rod design intended to work with higher-tension strings.

For more detail and cobverage of the 4002/4004 etc - there is a great article on the RickResource site - follow the links from the home page to "The Rickenbacker Registration Page" and then select "Articles" from the menu - you will find an article on Bass models. The 4000 series is described in detail on the second page. Sorry - my browser won't display the direct link for some reason.

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As I get older, my music gets softer and my shirts get louder....

Thanks for the info Antipodean. I am currently in the market for another bass. It will be a help to have my terminology correct. Thanks again.