Would you please read this article and explain to me just what the hell is an alarm gun? Apparently, they are easily altered into real guns and, according to this blog post, they are becoming a problem in Europe:

As the E.U. cracks down on firearms, illegal trafficking in altered alarm guns is booming on the continent. They’re cheap, easy to alter, impossible to trace - so they are becoming the criminal’s weapon of choice.

Is it a fake or functioning gun rendered inoperable by having a sealed muzzle? I’ve just never heard the term before and a (granted — very quick) search on the internet hasn’t enlightened me.