The Chieftain Marksman was one of many possible configurations the GEC Marconi Marksman Anti-Air system could have taken, based on the FV4201 Chieftain hull. The Marksman was designed to mount obsolete tank hulls with a twin 35 mm Oerlikon turret, creating a system akin to the German Gepard in performance. While a prototype of the Chieftain Marksman was created and tested, the British Army ultimately opted against fielding the Marksman system, with Finland being the only operator of the system in the form of the T-55AM/Leopard 2A4-based ItPsV 90.

The Chieftain Marksman was introduced in Update 1.79 "Project X" as the earliest radar SPAA in the British tech tree. Noticeably slower than its contemporaries due to the underpowered hull, the Marksman is relatively ill-suited to the tank hunter role its ItPsV Leopard cousin is known for, although its excellent gun depression gives it an advantage when hiding behind terrain features. While its widely spaced guns and large, unarmoured turret make it vulnerable in close-range encounters, it is still lethal against enemy aerial threats due to its capable radar and fast-firing guns.