Yep, this is a Contax G 28mm f2.8 Biogon mounted to a Leica IIIf. It's rangefinder coupled down to 0.7m and has full manual aperture and focus control, and comes with an M-adapter. This is the first time we have seen one of these conversions and we're having fun with it :)
The Contax G-Series lenses are among the sharpest on the market, and getting to use one on a classic 1950s LTM Leica seems almost impossible.