It has been a while since I used Leica M, but the lens you have will be the first of the three designs in which Leitz (now Leica) has offered the Summicron. Your lens has fairly normal contrast and I would start with the film manufacturer's rated speed and development time. This will not be far off. The contrast of the 3rd version of the Summicron (still current) is much higher, I found I had to downrate b+w film a full stop and cut development. I did a lot of press photography with a collapsible Summicron and a Leica IIIF about 35 years ago.