It sure as poop ain't a Nambu, (Gen. Nambu had nothing to do with it) but it is Japanese, the Type 94 (1934) pistol, chambered for the 8mm Nambu cartridge. They were originally made for export and are listed in some Japanese export catalogs of the 1930's. The guns were originally made with black plastic grips and were highly polished and blued. When war came, they were made for the Japanese armed forces, and were reportedly issued to Navy pilots as well as to some higher ranking officers. As the war went on, quality deteriorated.
In spite of the crude appearance, they are functional and fairly accurate. The sear bar (the dogleg shaped piece) is set into the left side of the pistol, and led to the WWII belief was that this was a "suicide pistol". Supposedly the Japanese soldier held out his pistol as if he were going to surrender it, then pressed the sear bar, either killing himself or an American. The story was nonsense, of course. No combat soldier would let an armed enemy get close enough to do anything like that, no matter how he held his pistol.
Jim