Identify a bayonet

[Electraclyde]

Can anyone identify this bayonet and which weapon it was used on. The blade is exactly 7" long, It attaches to the weapon like the bayonets that were used in WWI on the trench shotguns, i.e. they do not have a ring around the end of the barrel. they attached on a tab that was below the barrel.
The grip appears to be similar to plastic and is black. On the hilt of the blade are the initials "AFH" and below that is "U" flaming bomb "S"