No, this isn’t some new fetish man-gerie suit. Duofold’s Norse-Net was a Scandinavian-style knit underwear popular in the late 60s early 70s. It claimed to provide maximum ventilation in warm weather and maximum insulation (when air spaces are sealed by close-fitting outer garments) in cold weather.
The ad in the photos is taken out of Backpacker Magazine Issue 3, Fall, 1973.
Basecamp Vintage & Archives 