http://www.rockislandauction.com/viewitem/aid/67/lid/1639

The Type 100 (sometimes called the Type 0) was one of the initial Japanese experiments in paratroop rifles. Manufactured from standard Nagoya Arsenal Type 99 rifles, the Type 100 used a set of interrupted lugs at the chamber to allow the rifle to be broken into two short sections. Only a few hundred of these were manufactured for testing, and ultimately the Type 2 design (with a locking wedge) was adopted instead.