Here is an absolute oddity, a WW2 Imperial Japanese made stainless steel Shin Gunto in Army Mounts which leads me to believe this was a Marine Landing unit or Army unit attached to the Navy officers weapon. These were made in small amounts for soldiers who were going to be carrying them at sea, in the sea (as in jumping from landing or beaching craft) or in very humid areas such as the smaller islands in the Indo-Chinese sea.
Whilst the unit designation of the owner remains open to conjecture due to the oddness of the mounts and blade the quality can't be denied. This blade has a beautiful straight hamon and its fittings still retain a lot of the gilt that has so often worn away. This sword can be yours for £995 or best offer.