The board of trustees of the police and firemen's retirement system of New Jersey shall accept as a member of the retirement system any policeman, otherwise eligible for membership, whose appointment is confirmed pursuant to this act provided there is paid into the retirement system, in such manner as the board shall prescribe, the contributions that would have been payable had he been so appointed at the age of 30 years.
N.J.S. § 40:47-20.11