Could 1971 be near the first time that an extruded rim was produced for a bicycle? I could be quite wrong, but I can't recall any extruded doublewall rims, such as the 1320s, prior to this, with tubulars of that era being formed from aluminum tubing, and alloy clinchers, such as Benelux, being apparently formed (in this case rather poorly) from aluminum strip. The Super Champ Model 58's are, with their twin-hollow extrusion, the earliest extruded rims that I'm familiar with, though Nisi Evian and others were common by the mid-1970's, and, wait a minute here, a second look at these 1972 Weinmann singlewall rims shows a welded seam but I can't really tell if it's extruded or formed from strip.
David Snyder
Just wondering in Auburn, CA
"The Gitane was the first to be delivered in October of 1971 and per his request for "...suitable clincher rims" (...the LBS had told him that he would not be allowed to specify a particular make or model in this regard) it came fitted with a set of 700c Rigida 1320 double wall Rigi-ALU polished aluminum rims having a 20 mm section and a hooked bead rim profile."