I found it here as well. Looks like the design goes back to 2003.

http://www.specialized.com/us/en/bc/...0&menuItemId=0

Checking the 2003 Allez models, I don't see any that come spec'd like this. So it must've been built up by the frame..

Does $599 seem reasonable? I'm thinking of offering $450 based on it's age and spec.