AKA: MC-4. Status: operational 1958.
The MC-3 and MC-4 series of suits used the MB-5, MA-2 (ILC Dover) and MA-3 (Bill Jack) helmets.
The MB-5 helmet was virtually indistinguishable from the improved K-1 or MA-2 helmets except for AIC-10 headset. Later developments following the original partial pressure suit helmets resulted in the very different appearing MA-1 and MA-3 series helmets, which were far more comfortable designs that integrated helmet internal protection and sizing components into a single assembly (featuring a moveable transparent visor) that could be worn with both full pressure and partial pressure type suits. Ironically, developments of ensuing decades would come full circle with a return from the 'long-term' survival concept that was then taking hold, to the original 'get-me-down' idea which had produced the earliest partial pressure designs.