Fiat 521  The Fiat 521 is a passenger car produced by Fiat between 1928 and 1931. The 521 was derived from its predecessor model, the Fiat 520, but with a bigger engine and chassis. The 521C was a shorter variant. This car was produced outside Italy, most notably at the Fiat-NSU plant in Heilbronn, starting in 1930, setting Fiat on the path to its subsequent multinational status. More than 33,000 Fiat 521s were produced in Italy and Germany.