I agree Due Ruote. 1975 , I'd say. The Silver Lilac color was only mentioned in the 1975 catalog, as the only option. May have been available in '74, but the specs say nothing about colors. In 1976 only silver is mentioned. And yes, OldBike, that Philippe stem is original to the bike. Catalog page from Stronglight's collection on Flickr.
http://www.flickr.com/photos/strongl...57602014094812