Section 28A. Notwithstanding any general or special law to the contrary, in any city or town which accepts this section, no person shall be eligible to have his name certified for original appointment to the position of apprentice lineman in a municipal light department if that person has reached his thirty-second birthday on the date of appointment. A veteran shall be allowed to exceed the maximum age provision of this section by the number of years served on active military duty, but in no case shall a candidate for appointment be credited with more than 4 years of active military duty.