Here is a website with a Shimano Time line that some may find helpful.
It includes the date of intro of the infamous SkyLark Derailleur and Duracci componentry.
http://corporate.shimano.com/
I had a British Norman Fay racing bike set up with all original Dura-Ace Black anodized parts.
That stuff was the bomb!
Donald F. Dunstan
Winters, TX