The picture is not very clear (out of focus) and a couple more perspectives would help. Having said that, I understand the stud is threaded some thing like 10-36 and I imagine the hole in the center is threaded. I believe the hole is for the cap screw which prevents the the slide lock lever from unscrewing all the way. If I am correct then for it to actually work effectively the cap screw thread would be left hand so I would check that out. I am guessing here as I have never actually taken one apart. If it is left handed then it should mention that in the Lyman paperwork. Question: as you want the slide lock lever when tightened pointing down I wonder how Lyman timed the threads to achieve this?
Another minor comment I believe the slide stop is installed upside down on this sight.
And last, there is a shadow line around the front and bottom of the base in the wood. Looks like the wood was cut larger then needed initially and it was repaired with a very good job of "repair". Curious if I am seeing this or my old eyes are playing tricks on me.
