No person shall be admitted to an examination for promotion for the various job classifications in the police and fire departments until such person has met the minimum qualifications of education and experience as specified in the job descriptions and served under regular appointment in the city of Aberdeen including probationary period; provided, however, that in the event the position to be filled is one requiring specialized or technical training or skill, of which fact the civil service commission shall be the judge, the commission may permit all members of the department, regardless of time and service, or persons nonmembers of the department, to take such examination. An exception to the examination restriction shall be granted to regularly appointed members who will meet all the minimum requirements of education and experience for promotion as specified in the job descriptions prior to the expiration of the eligibility list that results from that examination; provided, however, that no such member shall be promoted until all stated requirements are met.