Bob and Chuck,
I am the original owner of a 1979 Benotto Mod. 3000. It is made with Columbus SL tubing, Nervex lugs, semi-sloping fork crown, diamond shaped stays (both). The only braze-ons are for the levers, bottle, brake cable, and derailleur cable guides. I spoke to Benotto at the 1980 New York Bike Show. He said the diamond stays were the idea of Merkx. That Benotto/Derosa is an interesting bike. I think it is mid 80s. Also, consider the possibility that the fork came from another bike??
Michael Allison
NYC