Panzer II variants the Pz.Kpfw. IIJ, it was redesigned after the Panzer V Panther, most noticeably with the introduction of fully sloped frontal armor. Two versions were initially planned, a lighter, faster 18-ton variant and a slower, 26-ton vehicle; the former was abandoned at an early stage. Subsequently, work on the first prototype was abandoned when it was determined that the vehicle was underarmed for its weight, and versions of the Panzer IV and V could serve just as well in the reconnaissance role while being more capable of defending themselves. This vehicle never received an official Panzerkampfwagen title, but it would have
AI Mk. IV radar looking up from the display at the last minute, and the system was used only experimentally. By this time the microwave units had started to arrive in small numbers, so Mk. V production was repeatedly delayed pending their arrival, and eventually cancelled. Starting in the summer of 1942 the TRE development team began experimenting with systems to project the display onto the windscreen, and by October had combined this with an image of the existing GGS Mk. II gyro gunsight to produce a true head-up display known as the "Automatic Pilot's Indicator", or API. A single example was fitted to