There seems to be at least three variations of Ithaca Flues Model frame profiling.
Likewise some have a screw in the top-lever attaching it to the spindle and some have the top-lever and spindle forged in one.
Kinda like there are two different Parker Bros. hammerless receiver profiles and there are press-fit pins holding the roll and those with the slotted head screw two-piece pin to hold the roll.