The FN 4RM/62F AB light armoured car was developed by the now FN HERSTAL SA to meet the requirements of the Belgian Gendarmerie and is based on the chassis of the FN 4RM/62 Ardennes (4 × 4) 1500 kg truck.

The first prototype was completed in 1962 with the second following in 1965. Between 1971 and 1972 62 production vehicles were built. FN HERSTAL SA is no longer involved in the development or production of armoured vehicles or trucks.

The hull of the vehicle is all-welded steel with the driver seated at the front in the centre. The driver is provided with a single piece hatch cover that opens upwards, in the top of which are three periscopes and in the lower part a bullet-proof window with an armoured cover. There is a single door in each side of the hull; the door on the right is fitted with a rectangular observation port.

The all-welded turret is in the centre of the hull with the gunner on the left and the commander, who also acts as loader, on the right.

Both the commander and gunner are provided with a single piece hatch cover that opens to the rear. The commander has eight periscopes and the gunner has three, plus an optical sight linked to the main armament. Turret traverse is electric, two-speed (fast and slow) with manual controls for emergency use.

The engine compartment at the rear of the hull is equipped with an automatic fire-extinguishing system. Standard equipment includes an NBC system, searchlights for both the commander and gunner, and channels for crossing ditches carried on the rear of the turret (on 90 mm gun model only). The vehicle has no night vision equipment and has no amphibious capability.

This variant is armed with a 90 mm CATI gun which fires two types of ammunition, HEAT and shrapnel. The HEAT round weighs 3.5 kg and has a muzzle velocity of 640 m/s and an effective range of 1000 m. The shrapnel round weighs 5.1 kg, has a muzzle velocity of 330 m/s and a maximum effective range of 1800 m. A 7.62 mm MAG machine gun is mounted coaxially to the right of the main armament and a similar weapon pintle-mounted in front of the commander's cupola is used for anti-aircraft defence. Mounted on either side of the turret at the rear are six electrically operated smoke dischargers.

This model is armed with twin 7.62 mm MAG machine guns and a 60 mm breech-loaded mortar which can be elevated separately or in parallel.

It is not fitted with an anti-aircraft machine gun and the smoke dischargers are towards the front rather than the rear of the turret as in the case of the 90 mm gun model.

This was a project only and was never built.