This is what I have found:
“On twin-tumbler gearbox models a choice of three headstock spindles was
offered: whilst the Series L had a 11/16" hole through the headstock spindle and
a 1.75" diameter, 8 t.p.i spindle thread the Series XL could be ordered with a
spindle having a bore of 13/8, a nose diameter of 2.25" with 8 threads per inch -
or a much safer and more rigid American long-nose taper in an L00 size.”
