I'm fortunate enough to own 1 Serenar chrome, 3 Canon chrome and 1 Canon black lenses. They are all excellent performers.
According to Peter Kitchingman's new book on Canon lenses, they are all the same formula and coating. The black lenses are quite a bit lighter, but many prefer the heavier chrome mount. Serenar was the first name given to the Canon lenses, but all are 1st quality, regardless of age. The coating is hard, unlike the early Leica lenses. Small cleaning marks (a euphemism for scratches) on the front element has basically no effect on images.
The lens looks good and handles well on an M3, or any of the several Canon RF models. The Canon P is frequently touted as a poor man's Leica M, and is a beautifully made camera, with a full opening back and variable VF as bonuses.
If you get involved with the lenses, the book mentioned is a solid investment in any future purchases, and top quality in content and execution. Spoken as a very satisfied owner, with no other interest financially in the book. There is a good thread in this forum on the book.
Harry