This is a prototype of the Sonnetar 25mm f/1.1 lens for the Pentax Q mirrorless camera by MS Optical. Miyazaki san, the man behind MS Optical, has created some unique lenses in the past (for example the Perar Super Triplet 28mm f/4 and the 3.5/35mm f/3.5 lenses for Leica M-mount). Read the entire story at the Japancamerahunter (more pictures available on their flickr stream).
The Sonnetar 25mm f/1.1 lens was briefly listed on eBay for $650.
Here is another picture of the lens mounted on a Pentax Q body: