Detail of the helmet's headrest. It is inscribed with a large, red "III",
indicating that it is class III (non-flight, training-only) hardware.
Additionally, it is marked with "Use only with blue neck ring suits."
Apollo suits and helmets originally had matching blue suit and helmet neck
rings; these were changed to red to indicate a
change in the suit's vent port. The early Apollo A7L suits had the blue
hardware; NASA had switched over to the red-colored hardware by Apollo 11.
It would seem that this helmet, with its blue neck ring, is an older helmet
which was not associated with this Skylab A7LB suit but which was paired up
with it for display purposes.