To my knowledge, this is only existing Natura 24/1.9 converted for (LT)M-mount use. I had it converted as such because, while I enjoyed shooting with the Natura, I was frustrated by lack of control over focus/exposure/etc. This unique lens is faster than any other existing 24mm for Leica, and Leica's forthcoming 24/1.4, which promises to be astronomically expensive, will exceed it by less than one stop.
This lens was expertly mounted, by Ken Ruth (proprietor of Photography on Bald Mountain), into a Canon RF 50mm f/1.2 barrel. The barrel is fully rangefinder-coupled, with a second 'transfer focus' scale calibrated for the 24mm, allowing precise focusing from infinity to under one foot. The aperture is set wide open (why else would one bother with getting this lens, if not to shoot faster than f/2.8). The well made barrel has a useful infinity-lock, and nice smooth action, and the short housing is nonetheless much wider than the front element, making for a nice built-in shade. The rear element is long, so the lens does not mount on my CLE, but mounts fine on my M3.
