1 1/8" threaded headset forks had a shorter run than the 1" .
before un threaded 1.125" took over..

A stem fitting in a 9/8" fork is 1" in diameter,
matching the inside diameter of the steering tube.
25.4mm (headset wrench 36mm )

a 1" threaded fork the stem is 7/8" in diameter ..
22.2mm.. (headset wrench 32mm )