For your knowledge about the blank guns here in Scandinavia, Norway and Finland blank guns are free of 18 years of age so long as they are top-firing. As far as i know they are not allowed for self defence there. Dont know the rules in Denmark.
In Sweden (since 1985) you need a license for blank guns no matter if they are top-firing or front-firing, PTB or not. You cannot drive into Sweden with a blank gun in your car, and they are NOT to be used for self-defence here.
You only get a license for the guns here "if the owner has a special need for the blank gun/guns in question, such as sports, dog-training or collecting".
/// Daniel