Which of the following is NOT deemed a prohibited offensive weapon?

In Pennsylvania, a registered firearm is not considered a prohibited offensive weapon. This is primarily because registered firearms are legally owned and regulated under state and federal laws, provided that the owner has complied with all legal requirements for firearm ownership. The regulation of firearms typically involves background checks, licensing, and registration, which distinguishes them from offensive weapons that may not comply with such regulations.

Dagger, razor blade, and machine gun, on the other hand, can fall under the category of prohibited offensive weapons in certain contexts. A dagger and a razor blade may be considered weapons if they are intended to be used for aggression or violence. Machine guns, while also firearms, are heavily regulated due to their potential for mass destruction and their designation as prohibited weapons in many contexts unless specifically licensed. Thus, the nature of ownership and regulation surrounding firearms is what sets registered firearms apart, making them acceptable under Pennsylvania law in contrast to the other options listed.