The M1 was a two-axle railbus built for the narrow gauge network of the FCL. The first batch was created in 1933 to replace steam traction and had a 125 hp OM-Saurer diesel engine mated to a manual gearbox that drove the rear axle. With only one cab, they had to be turned at each end of the line. Only one of the first batch was built as M1c with rack drive. On flat sections it could reach 100 km/h too, but on the rack section the speed was restricted to 22 km/h. The following two batches came from different manufacturers. The second only had a power of 100 hp, while the third batch consisted of ten M1c with 130 hp. 

Between 1948 and 1953, some of the 45 vehicles were stretched and modernized. The wheel base and the total length both grew by 1,400 mm. Power now came from a 160-hp two-stroke Detroit Diesel engine. Withdrawals of the conventional rail buses were completed in the seventies after they had either been replaced by more modern rail cars or their lines were closed. The last M1c was replaced by a locomotive in 1981.