N.J. Stat. § 43:7-8
For the purpose of this act, the words "prison officer" mean and include any prison officer, reformatory officer, farmer guard, disciplinarian, identification prison officer, center keeper, marshal, superintendent, chief deputy, head farmer, herdsman, truck farmer, commissary officer, any uniformed officer, trade instructor, and any employee who has the custody of inmates in State penal institutions. No person employed on or after January 1, 1960 shall be eligible for membership in the Prison Officers' Pension Fund.
Membership in the Prison Officers' Pension Fund shall continue for any present member as long as his position, from whence he holds membership in the fund, continues to be in the State Department of Institutions and Agencies.
"Average final compensation" shall mean the average annual compensation for which contributions are made by a member to the fund for the 3 years immediately preceding his retirement, or in the event that he has been contributing for less than 3 years, the average pay he received during the time he was a contributing member.
N.J.S. § 43:7-8