Mk IV helmet
Mk IV helmet was a combat helmet used by the British Army in the 1950s to 1980s. It replaced the Mk III helmet and became the British Army's last metal helmet when it was replaced by the composite material Mk 6 helmet in 1985. Design. The Mark IV helmet was a modified design of the Mk III helmet with the chinstrap rivet moved down the bottom of the helmet shell as well as the introduction of fastener for the inner liner.