This is the American version.
It's an 8 shot .22" S&W rimfire.
I wonder if dropping a million or so Liberators in Iraq would have any useful effect?
They also come configured with a knife.
The most common however , is the garden vairety brass knuckles (incidentally they can be made of any metal, they were originally brass, thus the moniker) without attachments.
In New York they can still be purchased in martial arts supply stores and various stores where they sell security paraphenalia and supplies.