Leica Summicron-m rigid 50mm f/2 - uneven front element ring & glue marks?

I purchased this lens about 2 yrs ago, immediately sent it to Youxin Ye for a CLA. I've used the lens without any obvious issues since but one thing I had always noticed was what looks like an uneven black ring surrounding the front element of the lens. It's not perfectly centered to match the outer rim of the lens and there are glue marks visible.

I don't believe I ever took a close look at the lens before having it CLA'd but it seems unusual to see something so off center like that on any lens let alone one from a brand so highly regarded for their precision.

Any ideas as to what this is?