A Brief History of the Marque
Manufactured: 1926-1930 
Presented at the Turin Motorcycle Fair in 1926, the first Dardo motorcycle had a horizontal single-cylinder engine and entered production towards the end of that year.
Two versions were offered, Standard and Sport, with two-speed engines of around 125cc. These were followed by an entirely new motorcycle for 1928 with a tubular frame fitted with an OHV 175cc engine.
The horizontal cylinder had a hemispherical combustion chamber, a feature much vaunted on certain American automobiles built many decades later. These models were produced from 1929 to 1930, when the factory closed.
There are also records of a 50cc Dardo bicycle attachment engine produced in Bologna between 1946 and 1949. (Motociclismo gives 1949-51)
Notes. 1. Tragatsch gives dates of 1924-29.