"If my observations are correct the way that the air hoses
work is that the end of the air hose has a rubber grommet
(doughnut) in a cavity in the glad hand."
What you are referring to as a "gland hand" is called the air brake hose
coupling which was fitted into and clamped to one end of the brake hose
(22-1/2'' long x 2-1/8" O.D.) while the other end of the hose was fitted over
and clamped to the air hose nipple, also cast in malleable iron. The
"grommet" was the air brake hose gasket.
The nipple was threaded into the angle cock which was equipped with a
"glad hand" in order to open or shut off the air flow. Though there were
dimensional specifications for the angle cock - no call out was made for the
material used in their manufacture. Angle cocks were positioned at an
angle of 30 degrees ( /) while looking at the end of the car.
Circa 1943 (slightly revised from 1939) preference for the center line of
the air line was 2-1/2" below the center line of the coupler and 12" to
the right of center. The location of the angle cock from the end of the car
was to be 15" from the pulling face of the coupler (back) to the center of
the glad hand.
All location dimensions were in relation to the coupler, not the car body
itself, and it was permissible to jockey them, though minimum and maximum
dimensions were established (and revised) within the formula developed by
the MCBA and modified by the ARA and AAR.