After the initial production run of the Fiat 702, the 702A was introduced in 1920.

The 702A was visually identical to the 702, with the exception of the PTO pulley diameter having been reduced for better torque characteristics, and the return of the 18BL engine of 5.652 cc used in the 702 prototype, now developing up to 25 hp at 900 rpm. Up 5 hp and 100 rpm from the original.
Though the fundamental mechanical specifications seemed unchanged, the tractor gained 100 kg from its 702 successor, suggesting further strengthening of the casings and/or mechanical components 
had been undertaken.

In an attempt by Fiat to broaden the market for their 702A, the tractor was also converted and sold to railroads, factories and ports as the 702AF. The conversions meant the tractor could run comfortably on roads with solid rubber wheels, or on rails with converted steel wheels, with the intention of moving railway rolling stock in factory sidings or ports, and arranging trams. The special wheels and two massive bumpers for rail cart handling, took the weight of the 702AF to around 4.000 kg.

In 1923 the 702B was introduced, and being a more powerful upgrade of the 702A, meant the return of the bigger 18 BLR truck engine from the 702 production model.
Displacement was slightly increased over the 702 to 6.535 cc. Max power was unchanged, but the engine was now capable of running at 1.100 rpm. The weight also further increased, with 300 kg over the 702A. The appearance later changed as well, do to the new fully cast wheels.

The 703B was identical to the 702B, except for the addition of reduction gears in the rear wheel hubs. Though placed separate from the main gearbox in noticeable housings, the impact on the tractors performance when engaged were immense, increasing the towing capacity from 2.000 to 3.000 kg. 
And with farmers being able to disengage the reduction gears for faster ordinary haulage jobs, the 703 offered two tractors for the price of one. But of course was more expensive than the 702B.

The 702BN and 703BN had different carburetors, inlet- and exhaust manifolds to the other models, to accommodate lower quality fuels like fuel oil. Fiat did offer this as a conversion kit for the other 702 and 703 models.

The 702 and 703 were some of the most advanced tractors of their time. - But they didn't come cheap.
Adding to that the economic instability and inflation in early 1920's Italy, and the Italian governments liquidation of the state ploughing program, which flooded the Italian market with cheap second-hand American tractors, meant the 702 A/B/BN and 703 B/BN never made an impact in its home country.

The 702A only sold 627 units, and the 702 B/BN and 703 B/BN between 300 and 370 units.
Compared to the 1.100 units of the first 702.
 
The Fiat 702 and 703 did however manage a successful "tour de force" abroad.

Already selling cars and trucks abroad, the Fiat brand was well known, and Fiat decided to showcase their tractors in towing and ploughing competitions across most of the worlds continents, winning many against a big field of competing machines and concepts of the time.
One curious but effective trail organized in Finland, involved the towing of 35 tons of timber on a sled, in snow and freezing temperatures. Which the 702B did successfully.
 
At the end of 1925, the Fiat tractors were better known abroad than in Italy.