In 1974, Cockerill Mechanical Industries decided to reenter the defence market by producing a 90 mm gun system suitable for light and medium tanks and armoured cars.

The Mk I was followed by the Mk II which differed mainly in having a revised recoil mechanism which increased the length of recoil from 300 to 500 mm to reduce the trunnion force. The Mk III MA1 was introduced in 1986 and has a single-baffle muzzle brake. The Mk I and Mk II weapons are no longer in production.

Ammunition for these 90 mm weapons is available from a number of sources including MECAR, Royal Ordnance and Giat Industries.

All three Marks are similar in that they are manufactured from a special Electro-Slag Refined (ESR) steel, are light, and use a wide range of ammunition. All three guns use a triple-baffle muzzle brake (except the Mk III MA1 which can fire APFSDS-T projectiles). The Mk III gun has a breech mechanism for recocking in the event of a misfire; the Mks I and II do not. Other improvements with the Mk III include the reduction of recoil forces from 13,000 kg to 8,500 kg and the introduction of an improved ESR steel to reduce the incidence of barrel cracking. The recoil mechanism is hydroconcentric using two concentric springs, a light but very effective system which enables the large calibre gun to be mounted in vehicles weighing as little as seven tons.

Mk III in production. Used or trialled on Textron Marine & Land Systems LAV-150 and LAV-300, Panhard Sagaie 1 (Hispano-Suiza turret), Giat Industries AMX-13 light tank, Alvis Vehicles Warrior (CM 90 turret), United Defense M113 series (CM 90 turret), Steyr SK 105 light tank (CM 90 turret), AV Technology Dragoon, MOWAG Piranha 6x6 and 8x8, Alvis Scorpion, SIBMAS, Alvis Vehicles Simba, IVECO 6616, Renault VBC 90, Steyr-Daimler-Puch Pandur, PT-76 light amphibious tank, SANTA BARBARA BMR-600, Henschei Wehrtechnik TPZ 1 and Henschei Wehrtechnik Condor. By early 1999 more than 2,000 of these weapons had been produced by Cockerill or its licensees. They have been supplied worldwide on all continents except Australia.