Unsure if my contribution will provide clarity or confusion, but here goes.
There are two companies, Lee Precision (current) and Lee Custom Engineering (now dissolved).
For various reasons, Lee Custom Engineering became MEC (Mequon Reloading Company). Richard Lee went on to found Lee Precision after that and carried his designs over.
A lot of Lee Precision products are simillar but not exact copies of their old Lee Custom counterparts. The trimmers, case length gauge, shell holders and lock studs are just one example.
Lets look at the trimmer and case length gauge first.
The silvery case length gauge on the left is LP (new) whereas the one on the right is LCE (old) is darker. Note the end of the gauge being near flat on one and well bevelled on the other.
Now onto the lock studs and shell holders; as above, new on left, old on right.
Personally, I prefer the old setup as the lock stud has a flat base. This allows you to exert *slight* downward pressure whilst holding the locked case with one hand and gently turning the cutter with your other hand. This is a secure way of doing it, but slow. The new method which involves a drill can sometimes result in the case 'camming out' of the shell holder if you don't do things correctly. Don't get me wrong, it still works but not my cup of tea. Hence,
@Dr. Strangelove is getting it for free.
The new stud is an assimilation with an older accessory, the case spinner, which would attach to the lock stud and work in the same way.
The new shellholder is actually an improvement on the old design, slightly heavier but seems more robust. It is also radiused on the edge to allow a case to slip in more easily. Both threads are the same, so I use a new shellholder with an old cutter and lock stud. Trim length comes out exactly the same on either system.
Hope this is of interest to some.