A member of the fund who is an employee of the police department of a municipal corporation, who has resigned or has been honorably discharged from membership in the fire department of the same municipal corporation, and who is not a participant in the deferred retirement option plan established under section 742.43 of the Revised Code shall, in computing years of service in the police department under section 742.37 or 742.39 of the Revised Code, be given full credit for time served in such fire department, provided the member has paid into the Ohio police and fire pension fund a sum equal to that which the member would have been required to pay, under former section 741.12 and section 742.31 of the Revised Code, as a member of such fire department during the years for which service credit is claimed had the member been contributing a percentage of the member’s salary to a firemen’s relief and pension fund or to the Ohio police and fire pension fund as provided by such sections during such years.