N.J. Admin. Code § 13:54-5.5
A retail or wholesale firearms dealer licensed pursuant to this chapter may maintain large capacity ammunition magazines at its licensed premises for sale or disposition to another dealer, the Armed Forces of the United States or the National Guard, or to a law enforcement agency, provided that the seller maintains a record of any sale or disposition to any of the afore-mentioned entities, including a description by make and model of the large capacity magazine. The record shall include the name of the purchasing agency, together with written authorization on the official letterhead of the Superintendent, chief of police or highest ranking officer of the agency or the appropriate ranking military officer, the name and rank of the law enforcement or military officer authorized to make the purchase, and the date and time of the sale or disposition. A copy of this record shall be forwarded by the seller to the Superintendent within 48 hours of the sale or disposition.
N.J. Admin. Code § 13:54-5.5