If you want to use one of these on a Leica M camera, it might be easier to find the LTM version (like the one pictured) and use a simple screw-to-M adapter, right? The screw mount version was the one I had; used it on my Canon VI-T, which has a 100mm frame line that was close enough. I used it on a monopod (taking advantage of the built-in tripod mount, which later models didn't have) for theater photography. One frustration: the tripod mount is fixed in place (although slotted so you can find-tune its position a bit) so if you suddenly wanted to shoot a vertical, you'd have to frantically unscrew the camera and lens.
I shot a lot of pictures I liked with my 105/2.5 — I especially liked the contrast and texture — but after I got a 100mm f/2 Canon, I concluded it was just as good, plus lighter and a half-stop faster, so I kept it and traded away the 105/2.5. Still, super-nice lens to use well worth having!