The original series, built from 1937 was fitted with solid tyres.   Pneumatic tyres were introduced in 1940 and this occasioned the need for a spare, which was mounted on a carrier at the rear.    TL37s saw action in the desert, Tunisia and Sicily - as well as with the Italian forces in Russia.   After the Italian surrender in September 1943, large quantities of Italian equipment, including TL37s, were taken over by the Germans.