Sec. 6. MEMBERSHIP IN PENSION FUND; ELIGIBILITY. (a) Any person who has been duly appointed and enrolled as a policeman or fireman of any city covered by this Act shall automatically become a member of the pension fund of such city upon expiration of ninety (90) days from date such city comes within the provisions of this Act, provided such person at the time of such appointment was not less than eighteen (18) years of age and not more than twenty-nine (29) years of age and except as provided under Section 10A of this Act. In all instances where a person is already a member of and contributor to such pension fund, he shall retain and be entitled to all rights and privileges due him by virtue of having been such a member and contributor.

(b) Any person not a member of the pension fund when this Act becomes effective, who thereafter is duly appointed and enrolled as a fireman or policeman of such city shall automatically become a member of the pension system as a condition of his employment provided such person at the time of such appointment was not less than eighteen (18) years of age and not more than twenty-nine (29) years of age and except as provided under Section 10A of this Act.