In France the ETAT railway company made in the thirties some modern passenger cars with a round body which did not need a frame. Because of the form this cars were called Voitures Saucisson (Sausage cars). Both JEP (cast metal) and BLZ (sheet metal) made this cars in H0 gauge some 70 years ago and Hornby made these in tinplate in 0 gauge before WW2:
Here is a video of the H0 cars with the matching JEP and BLZ locomotives:
Regards
Fred