The Voigtlander 40mm f1.2 lens in M mount is identical to it’s Sony FE variant, but rangefinder coupled
A little while ago, Voigtlander released a brand new Voigtlander 40mm f1.2 manual focus lens for the Sony E mount; but just recently they announced it for the Leica M mount. This lens is nearly identical optically to the Sony E mount version but the Voigtlander version is cosmetically different to accommodate more of the rangefinder crowd. Additionally, the M mount version is rangefinder coupled. Of course, this also means that you should ensure that your rangefinder can work well with lenses that focus down to that shallow of a depth of field. Of course, you could always zone focus too; but the point of having a lens like this is to shoot at f1.2.