The rod brake Superbe was a top of the line bike in British line in the 1950s. The more common Superbe/DL23 is the upgraded Raleigh Sports/DL22. However, the earlier, British line of Superbes (Dawn Superbe etc) were top of the line rod brake roadsters that usually had a dynohub, full chaincase, dry batter unit, and front mudflap. They have a sort of "Rolls Royce" element to them.

I still think this site is the best for learning about them:

http://sheldonbrown.com/english-3.html

Sheldon Brown devoted pages to both English 3-speeds in general, as well as Raleigh-specific 3 speeds. Sheldon's site helped get me started doing all my own work on 3 speeds maybe 9 years ago or so. It has what you need to get started.

http://sheldonbrown.com/retroraleighs/

There are also some catalogs there.

http://oldbike.wordpress.com/

There's a nice blog with some good pictures too.