This camera was the Prototype Leica MP made exclusive for the Japan Market and only 250 units made out of the factory, making it extremely rare and collectible.
The MP-6 was basically the same as a regular MP, but it comes with the classic vulcanite leather found on the older Leica cameras, a Leica Camera AG Germany engraving on the top plate and on some of the later models an M6 iso selector. These simple cosmetic differences may not sounds like much, but they really make a difference and are instantly noticeable. They set the camera apart from the regular MP.