A mid-40s Herse Competition is very light for a stock, unmodified road bike. Right around 20 lb with tubulars, a single front ring, no front derailleur, alloy saddle, alloy rear derailleur, Herse cantilever brakes, Herse alloy crank and hollow bottom bracket. The 18 lb quoted must be without tires, or with special lightening modifications. The bike in the photo would probably be just over 20 lb, with the steel rail saddle. The Competition frame uses lightweight Vitus tubing and weighs about the same as a Reynolds 753 frame.

Some French frame builders did make very light frames in the 40s and 50s. I have a couple (Cattaneo and Le Greves) that weigh within about 0.2 lb of the Herse.