It was a modern day (at least in 1959) Mountain Elmar. It was cheap at $79.50, cheaper than the 50/2 ($125) or 35/3.5 ($89.50). It was light at a mere 9 ounces. However, it was not popular, and only 2000 of them were built. An identical lens was built for Nikon F, and it wasn't popular in this mount either. Oddly enough, the lens was of preset design, which is no advantage without reflex viewing. This indicates to me that the lens was initially designed for the F, but was built in rangefinder mount while awaiting design completion on the camera.
Serial numbers begin at 408500 and run through 410500. Lens shade and front cap are 34.5mm clip on, and the lens uses 34.5mm filters.