Unfortunately, I couldn't find anything that defines "dagger" under New Jersey state law. Maybe someone else can help with that.
It appears that daggers, dirks and all that other good stuff listed in 2C:39-3 e. isn't just illegal to carry, but it's also illegal to possess, so you can't even have one in your house. (State v. Jose Alvarez, 1999 N.J. Super.)
The knives listed in 2C:39-3 e. are "weapons per se", meaning that they are considered by the law to be specifically designed as weapons. Other types of knives could be illegal under 2C:39-4 d.:
Other weapons. Any person who has in his possession any weapon, except a firearm, with a purpose to use it unlawfully against the person or property of another is guilty of a crime of the third degree.
or 2C:39-5 d.:
Other weapons. Any person who knowingly has in his possession any other weapon under circumstances not manifestly appropriate for such lawful uses as it may have is guilty of a crime of the fourth degree.
It seems that if the knife isn't of the type that is listed in 2C:39-3 e., you can carry it openly or concealed as long as you don't intend to use it for unlawfull purposes. It would be extremely difficult for a prosecutor to prove that you intend to use it unlawfully unless you confess or you actually do use it unlawfully. See State v. Jimmy Lee Riley, 1997 N.J. Super. for more about this.
2C:39-6. f. (2) and (3) list specific exemptions, but I believe that you can still carry a knife even if you don't meet the conditions there. As long as you don't intend to use it unlawfully, I don't see a problem.
Keep in mind that this stuff is just my personal interpretation of NJ law and I could easily be wrong.
