§ 54. Age requirements. Notwithstanding any provision of law to the contrary, except as herein provided, neither the state civil service department nor the state civil service commission, nor any municipal civil service commission shall prohibit, prevent, disqualify, or discriminate against, any person who is physically and mentally qualified, from participating in a civil service examination or from qualifying for a position in the classified civil service, or penalize any such person in a final rating by reason of his or her age; and any such rule, requirement, resolution, regulation or penalization shall be void. Nothing herein contained, however, shall prevent the adoption of reasonable minimum or maximum age requirements for open competitive examinations for positions where it is determined by the department and approved by the commission that such age requirements would be reasonable minimum qualification for such position. Minimum age requirements shall in no case prohibit an applicant who is within six months of the minimum age requirement from taking any competitive examination. Nothing herein contained shall be construed to prohibit the disqualification, on account of age, of any applicant for a position who has reached the mandatory retirement age applicable by law to such position.