Originally Posted by
Doug Fattic
Andy a small correction. I think these one piece lugs were made by the Nikko company. They are bulge formed.
Yes, until the mid-80s most of the 4nn, 5nn, and 6nn series frames used one-piece, bulge-formed head tubes from Nikko. Starting in the mid-80s, they used one-piece cast head tubes from Signicast in Milwaukee. These can be distinguished by a "TREK" cast into the head tube "lug."