I've never seen one that wasn't adjustable.Look in this attached file.It's the same is Singer 111w,211w,Consew 225,226,255,Juki 562,563.
441 top feed cam.pdf
I've found it's not good to buy a cheap hook,you get what you pay for,stick with a Hirose or Cerlani they should be close to $150.00,there are also some Juki 563 saddles on ebay that you should buy & then you won't have to machine yours.
I've wondered why myself & was always told they were made for sewing the vamps on a shoe.But it would be hard for a right-handed person to sew with so maybe they were specially made for left-handed people to sew in the shoe factory?
David,Looks like it's stitching pretty good.I wished I kept ser# of the Landis 3's I've sold over the yrs, because I'm almost certain I painted & sold this one many years ago,we used to paint alot of them this color & also used angle iron to hold them to the table.And we had a fellow come in one time that looked @ some machines in the warehouse house while any guy was there alone & alot of the plates & shuttles came up missing after he left, so we had them made up in bronze like this one has.
I can't tell you what was in someones head when they did this because I don't know of any reason other than maybe the last belt fit loose so they "tried" to make it tighter.I would take a Dremel & grind off the high points of punch mark & called it fixed.
I was working on a machine last Sat. that needed one & found out we are out of them,I will be ordering more soon.It is screw #200082.Here's a parts list for the machine herehttps://www.supsew.com/download/Singer/Singer 111W155.pdf
The stitching looks pretty good.Here's a pic of the collar on the inside of the handwheel it's just alittle under 3/8" & also a pic of the standard old style of hinges for an industrial machine,while the ones you have will work they are for a home machine & the pivot pin is much thinner.
111w flywheel.html
It's odd you have that much shaft sticking out,it's usually flush.There is a collar cast into the other side of the pulley is it on there?Yes the 2-screws are all that holds it to the shaft.
On the backside of the machine there's a wingnut adjustment that has L,M,H loosen the wingnut & move it so the line is on the H & report back what happens.
The circled cam controls the timing of the walking feet,almost all walking feet machines have & many times are not adjusted from the factory correctly.
441 top feed cam.pdf