Eligibility service for a member consists of service credit:
(1) for employment as a member;
(2) regained under § 25-304 of this subtitle by a member who redeposits accumulated contributions previously withdrawn;
(3) transferred from a retirement or pension system under Title 37 of this article or Title 31, Subtitle 1 of this article;
(4) for military service as provided in Title 38 of this article;
(5) purchased under this subtitle; or
(6) transferred from the Employees’ Pension System under § 25- 306.1 of this subtitle.