The Fiat 500 is a car produced by the Fiat company of Italy between 1957 and 1975, with limited production of the Fiat 500 K estate continuing until 1977. The car was designed by Dante Giacosa.
Launched as the Nuova (new) 500 in July 1957, it was marketed as a cheap and practical town car. Measuring only 3 metres (~10 feet) long, and originally powered by a tiny 479 cc two-cylinder, air-cooled engine, the 500 redefined the term "small car" and is considered one of the first city cars.
Nuova (New) (1957–1960):
The 'original' new 500, the Nuova, has a smaller two-cylinder engine than all newer models, at 479 cc (500cc nominal), hence the name, and producing just 13 bhp. This model also features a fabric roof folding all the way back to the rear of the vehicle, like that of a Citroën 2CV rather than the later roof design, which only folds half way back along the roof. The Nuova is one of three models featuring "suicide doors". There is also a stylish Sport version of the Nuova, which features a distinctive red stripe and a more powerful engine, bored out to 499.5 cc from the original 479 cc engine, thus producing an impressive 21 bhp from the same original block.
Replacing the original Nuova in 1960, the D looks very similar to the Nuova, but there are two key differences. One is the engine size (the D features an uprated 499 cc engine producing 17 bhp as standard—this engine is used right through until the end of the L in 1973) and the other is the roof: the standard D roof does not fold back as far as the roof on the Nuova, though it was also available as the "Transformable" with the same roof as the Nuova. The D also features "suicide doors".
K or Giardiniera (1960–1977):
The estate version of the Fiat 500 is the longest running model. The engine is laid under the floor of the boot to create a flat loading surface. The roof on this model also stretches all the way to the rear, not stopping above the driver and front passenger as it does in other models of the same period. The K also features "suicide doors" and is the only model to continue to sport this door type in to the 1970s.
F or Berlina (1965–1973):
The F spans two periods of 500 production, the D and the L. As such, it is the most frequently misidentified model. Between 1965 and 1969 the F carried the same badging as the D, but the two models are distinguishable by the positioning of their door hinges. The D has "suicide doors": the F, produced from June 1965, at last featured front-hinged doors. Between 1969 and 1972 the F was sold alongside the Lusso model as a cheaper "base model" alternative. While the F and L are mechanically very similar, the key differences are the bumpers (the L has an extra chrome nudge bar) and the interior (the F interior is nearly identical to the original 1957 design while the L sports a much more modern look).
L or Lusso (1968–1972):
The penultimate model, the main change for the L is a much modernized interior (including a renewed dashboard) which brought the Fiat 500 up to date. Greater comfort and style were provided in this new model for the new generation.
R or Rinnovata (1972–1975):
The last incarnation of the Fiat 500 was the R model. It had a larger 594 cc engine, designed by Abarth, giving it a more usable power rating of 23 bhp, came with a syncromesh gearbox. The floor-pan which was from either the 'L', or later, the new 126. It was also more comfortable, but more simply trimmed and equipped than before — the fuel gauge was omitted and only the low fuel indicator remained. The 500 R was also a stop-gap for Fiat prior to the launch of the Fiat 126, and when the new 126 was launched, sales of the old Fiat 500 R plummeted. It sold alongside the Fiat 126 for another two years before Fiat retired the 500.
Source: Wikipedia, 2011