The procedures for heat treating each part and from year to year differed. The steels did change. So did the desired color and tint.
The complete instructions can be found here. I don't know why someone stuck them on Scribed, but you can read them all there fot free without having to get a $9 a month membership. All temperatures are in Centigrade.
http://www.scribd.com/document/15362...structions-pdf