Every participant in the Fund on the effective date of this amendatory Act of 1979 shall be deemed to have been a municipal employee throughout the entire period of his service during which he was a contributor and participant and for which period of service he is credited with the required contributions to the Fund for annuity purposes. The period or term of service credited shall be based on the applicable provisions of this Article relating thereto. Any past service credited or annuity granted to any participant and contributor prior to the effective date of this amendatory Act of 1979, based on the service of any participant and contributor prior to or subsequent to the effective date of the “Municipal Personnel Ordinance” of Chicago or the “Illinois Municipal Code” relating to civil service of cities, shall be deemed validly credited or granted for all purposes of this Article.