[4] In 1980 an upgraded model, the GDF-002 was produced, which featured an improved sight, and the ability to be directed by an off-gun digital control system.

A few years later a third version of the system was being produced, the GDF-003, which was broadly similar to the GDF-002, but included some enhancements like self-lubricating weapons and integrated protective covers.

[6][7][8] In 1985 a further upgraded model was produced, the GDF-005, which was introduced, featuring the Gunking 3D computer-controlled sight with an integrated laser range-finder and digital control system.

Development of the KD series cannon began around 1952 soon after Oerlikon calculated that 35 mm was the optimum calibre for an anti-aircraft gun.

It's an all weather low to medium altitude (up to 3,000 m) air defence system with the maximum effective distance of 4,000 m. The Skyguard fire control system performs air surveillance, target acquisition, calculation of the derivative-action values and control of the twin 35 mm guns.

In Taiwanese service, the system includes the Sky Sentinel radar, one 35 mm Oerlikon twin gun and an AIM-7 Sparrow Missile Launcher.

[10] In Spanish service, Toledo is a Skyguard system with Aspide launchers where the fire control unit has been replaced with Skydor from Navantia.

[29][30] Norwegian ammunition was supplied to Ukraine in 2022 for use in the GDF guns in its Flakpanzer Gepard anti-aircraft systems, but it was found not to be compatible, requiring modification.