I noticed it while truing a customer's wheel,

I didn't install this sprocket.
The reason is (→here)
Even when I didn't install it, there are examples of installations
that follow the method in the linked post,
so aligned printing doesn't necessarily mean I installed it,
but if the printing isn't aligned, it definitely means I didn't install it.


Anyway, about this lockring—
it's made by Popp Products (a Swiss high-precision cutting parts brand).
When I spin the wheel, this lockring
appears to be wobbling eccentrically,
so I figured it must be a top gear assembly issue
and removed the lockring.
It's a Shimano sprocket, but
with just the top gear, you can actually install it on the wrong spline
and the lockring will still thread on.
However, in that case, the top gear should also be eccentric.
But that's not what's happening...
I took a closer look to figure out what was going on, and



depending on the angle, the rim thickness varies so much that it just looks that way.