Japanese-Made M4 Bayonet for the M1 and M2 carbine, made by Kiffe in Japan. This is basically a copy of the U.S. WWII M4 bayonet, with the stacked leather grip and plastic end spacers, though without the holes in the bottom plastic piece to punch out the pins for the latch. It also does not have the starburst peened tang.
The bayonet is the Kiffe version made in Japan in the early 1960s for the civilian marksmen program as the US Government was selling off the surplus carbines of which there were many.