I have a middle-late 70's Super Corsa, ceramic headbadge, long point lugs w/ 3 hole cut outs. It has a 26.2 post. Whatta ride! Sheldon Brown says on his website:
"Sometime around 1983 it all ended. The 26.2 sleeved seat lug was replaced wit a different cast model that used a 27.2 post. The familiar 3 hole lugs were gone as well."
Does yours have the 3 hole seat lug?
-Dan Borden