Alright folks, I've updated my 500 history to reflect Dan/Panther's 1948 prototype. I still need help filling in all the blanks and question marks on my timeline though. My goal is to try to make my timeline as complete and authoritative as possible for ALL of the brands of 500's, including the licensed clones made by independents like ITT/Kellogg, Northern Telecom, and Stromberg-Carlson.
Here it is:
http://members.dslextreme.com/~zuperdee/telephones/500_history/we_500_history.html