Manipulating EXIF Info
The Leica M9 has no means of determining foreign or old lenses. The newer Leica lenses have a 6-bit (visual) coding mechanism for determining the lens. Problem is that this is only for (relatively new) Leica lenses. There is the possibility to manually select the lens in the menu of the M9, but that's only limited to the Leica brand lenses. No option for Carl Zeiss lenses.
For certain characteristics, and in-camera processing of the RAW image it's handy to manually select a Leica lens even though you've attached a Zeiss lens. This can be automated by coding the lenses yourself (or have Zeiss do it for €100 a lens).
All this is nice, but it still generates photos with faulty EXIF information, because you shot the photo with a CZ C-Sonnar 1.5/50mm and not with a Leica 1.4/50mm Summilux ASPH....