In addition to listing and claiming credit for prior services as a sheriff under paragraph (4) of Code Section 47-16-40, the applicant may elect to list and claim credit for service in the armed forces of the United States, not to exceed four years, and service as a peace officer other than as a sheriff, not to exceed four years, provided that he was employed during such period as a peace officer by the state, a municipality, or any other political subdivision of this state and was required by the terms of such employment, whether by election or appointment, to devote his full time to the duties of a peace officer. Upon approval or acceptance of such claims by the board, the applicant shall be credited with such service as a basis for future contemplated retirement, provided that credit for such service shall be available only if the applicant shall have served as a sheriff for a minimum of eight years subsequent to December 31, 1960, and subsequent to periods of service for which credit under this Code section is claimed; provided, further, that amounts due under paragraph (5) of Code Section 47-16-40 have been paid for such periods.