This is the Japanese model known to collectors as the Special Purpose Model of the Type 100 Japanese WWII bayonet. This designation is one that has been applied by post-WWII collectors. Recent findings of Japanese wartime documents, however, mention the title of this bayonet as the "Test Type One Knife Bayonet".
It was manufactured in the 1941-1942 period by Toyoda Automatic Loom Works factory under contract to Nagoya Arsenal. The maker markings were transferred to the top of the grip tang while the serial number 9560 is placed on the pommel end.
This bayonet was designed during World War II for paratroop use as an accessory for the Type 100 submachine gun and although unconfirmed is also reported as having been intended for use with the Japanese Type 2 Paratroop rifle (this is the take down model).