By 1967, Fiat was leading the European market, and its 50th anniversary was coming up. For the occasion, a new series was developed in Turin with more innovative characteristics than earlier models. The new series would be based on the Diamante series, and the name chosen was "Nastro d'Oro" or "Gold Ribbon", marking the "Golden Anniversary" of Fiat's "marriage to the land".

The appearance was a strong evolution of the Diamant series, again penned by Pinninfarina, with the longitudinal ribs of the engine cover now more predominant, and running though to the nose conferring lightness and movement. The colors were slightly changed as well, with a lighter orange for the bodypart, and blue for the mechanical parts, which gave the impression of a dynamic and modern machine. 

The new series wasn't only a styling exercise though. The series introduced new upgraded engines, all now with direct injection and rotary injection pumps, and all but the smallest reverting to a stressed crankcase design. Improved driving ergonomics, a number of new safety features including a lock preventing starting the engine while in gear, new 12 volt electrical system, upgraded gearboxes with synchronizers, and the control-matic three-point hitch now standard on all models, are just a few of the technical features to mention.

Some sources tell, that all models at launch had the option of a Frutteto, Vigneto and Granluce variant, though this has been difficult to confirm.

The first model from the Gold Ribbon series to be put into production was the 550. It used a four cylinder version of the 250's engine, and was the large-to-medium size tractor in the series.
The 500 and 540 came along in years after, as Fiat would fill the power-gap between their models.

The 500's were sold in Italy and internationally as Fiats, but in France still sold as Someca.
Someca being the agricultural arm of Fiats French subsidiary Simca.

All models used a stressed chassis design, with the engines cast-iron crankcase being part of the tractors backbone. 

The gearbox was an eight forward and two reverse, with the four heigest gears synchronized for all models. PTO and locking differential on the rear axle as standard. The model was also offered with draft control / "Control-Matic".

The 500 and 540 used a slightly tuned version of the three cylinder watercooled, direct injected diesel engine from the 480, with a displacement of 2.592cc, developing 50/54 hp 2.600 rpm, and 153 nm at 1.500 rpm / 160 nm at 1.350 rpm.
The 550 adopted a four cylinder watercooled, direct injected diesel engine, with a displacement of 3.119cc, developing 55 hp at 2.400 rpm and 200 nm at 1.500 rpm

The Gold Ribbon Series tractors enjoyed even greater success than its predecessor, being recognized for their new design, engines and features.
In 1968 alone, when the European market was contracting, Fiat produced a total of almost 60.000 tractors, 42.000 of which in Modena alone, 5.000 more than the previous year. That year also saw the production of the 500.000th Fiat tractor since 1918.