Unlike the Humber LRC Mark I and Humber LRC Mark II which had 4x2 drive, the Mk III used a specially designed four-wheel drive chassis, and went into production near the end of 1941. The Humber LRC Mk IIIA looked like a regular Mk III but had additional observation ports added to the front angles of the vehicles upper armor. The Mk IIIAs (sometimes converted from earlier marks) began to appear in 1943. Over 3,600 Humber LRCs of all marks were completed by the end of WWII.