Any employee who is not a member of and was not required by law at the time of appointment or employment, or at any time thereafter, to become a member of a contributory retirement system, may, at the discretion of his employer, be retired and granted a pension under the provisions of this act. No employee shall receive a pension under this act, if he is eligible to receive a pension for the same employment under any other law of this State.
N.J.S. § 43:8B-2