http://www.rockislandauction.com/viewitem/aid/67/lid/1632

Before the Type 14 Nambu pistol was developed to replace the "Papa" Nambu, Kijiro Nambu experimented with a high-capacity design with a 15-round magazine. This pistol was called the Type A Experimental, and was designed around 1920. Only 15 or 20 were made, and they show elements of both the Papa and the Type 14 (like dual recoil springs).