Navy Mk 4 Suit - Credit: USN. 14,476 bytes. 163 x 323 pixels.

By the early 1960s, the US Navy had progressed through a series of developmental models of the full pressure suit that would ultimately take final form in the Mark IV, Model 3, Type 1, a production suit which US Navy aircrew wore on high altitude flights during its cold weather operations.

Regardless of the success of the A/P22S-2 suit and its modifications in Air Force use, it remained to the US Navy's cooperative program with the B. F. Goodrich Company and pioneer suit designer Russell Colley to solve some important problems concerning mobility and full pressurization. One of the most important developments was an aneroid suit controller that maintained suit internal pressurization at precisely 0.24 bar. The Mark series of US Navy full pressure suits which followed culminated in three models of the final Mark IV suit, which went into production in 1958 as standard high altitude issue for US Navy squadrons. The Mark IV, Model 3, Type 1 suit featured various enhancements in fit and ease of donning, as well as substantially improved pressurization control. It would go on to be selected as the basic foundation for modification into NASA's early earth-orbital suit (the original Mercury prototype suits were specially reworked Mark IV suits).