Those are tubular rims. Clement 50s are sewup tires. The tires get glued onto the rims. Old style racing technology, still used by some pro racers because they are safer if you flat at high speed. I've got sewups on one of my bikes - been using them for 30 years. East Hill got a bike last year with sewup and has used them. The tires are sewn around a tube, so if you need to patch the tire, you cut stitching, patch the tube, and sew them back up. New tires can be found for $25-30 if you shop around online.