Way back I saw what could have been either Super Champion or Mavic relabeled as Schwinn Approved Tubular rims.
I would check the frame and fork to verify what the bike was constructed for, tubulars or 27" clinchers.

There were 700c clinchers back then, they were uncommon, Michelin was the brand we saw. A mechanic at the shop I worked for trained on 700c clinchers just to save $ and to feel fast when he swapped out for his race wheels.