I just got a blue Parker Super 21. I really like the way it writes, and am really happy with it (didn't pay much for it, either)

Celluloid pens are "purdy" but I like the utilitarian beauty of Parker 51/21. I know it is not considered as collectible since it was a cheaper line. I read info on Richard Binder's page, and some archives from Pen Trace. Is there any other place I can get information on 21 (such as colors made, etc)?
Taki