Mystery Japanese Semiauto

While in the Smithsonian gun room, I noticed a semi auto Japanese rifle of a type I have not seen reference to before. It is definitely Japanese, judging from elements like the split buttstock and rear sight, and the ventilated underside of the hand guard is reminiscent of the Japanese Pedersen rifles. However, this rifle uses a rotating bolt and a receiver design that I am not familiar with.

Has anyone seen this before? The tag on it said it was a Type 5, which believe was a mix-up with the rifle next to it on the rack (which was a Type 5 Japanese copy of an M1). Click on the photos to enlarge:

Buttstock
Buttstock
Muzzle
Muzzle
Ventilation on the underside
Ventilation on the underside
Magazine floor plate
Magazine floor plate
Top of the action
Top of the action