Alfa Romeo RM was produced between 1923–1925, it was based on RL

Alfa Romeo RL

The Alfa Romeo RL was produced between 1922-1927. It was Alfa's first sport model after World War I. The car was designed in 1921 by Giuseppe Merosi. It had a straight-6 engine with overhead valves...

 model. Car was introduced first time in 1923 Paris Motor Show and total production was around 500 cars. RM had 2.0 L straight-4 engine, which produced between 40 bhp to 48 bhp. As most of Alfa Romeo cars this was also used in racing purpose.
Three versions was made: Normal, Sport and Unificato. Sport had raised compression ratio and Unificato had longer wheelbase and slightly bigger engine.
RM top speed was around 90 km/h (55.9 mph).

Models:

• RM Normal, 1944 cc 40 bhp (1923)
• RM Sport, 1944 cc 44 bhp (1924)
• RM Unificato, 1996 cc 48 bhp (1925)

Alfa Romeo half track

A very rare half track version based on RM was built in 1920s. The half track used RM straight-4 engine modified to work with dry sump lubrication. The track used was Citroën Kegresse licensed, only one example is known survive.