This Voigtländer lens sports a Leica M mount. The lens has a maximum ƒ/2.8 aperture and a minimum ƒ/22.
From Photospecialist
Voigtländer Heliar 2.8/40mm Asph. VM Black Lens
WEX Photo Video
Voigtlander 40mm f2.8 Heliar Aspherical VM Lens for Leica M - Black