In addition to the supernumerary and regular police force in each city, there shall be an honorary grade, known as the veteran reserve, to which the police commissioners or police committee may, at its discretion, by a unanimous vote, with the approval of the mayor, transfer any member of the regular force who, through age, or physical disabilities incurred in the discharge of perilous duty, or in long and faithful service, becomes permanently disqualified for the more active duties of the regular grade; provided the pay of the members of the veteran reserve shall be regulated by the police commissioners or police committee in accordance with the amount of duty performed and shall not be more than one-half nor less than one-fourth of the rate of compensation previously received by such members while in the regular grade; and provided any member of the veteran reserve may be removed in the same manner as a member of the regular force. The board of police commissioners or police committee may, at its discretion, by the affirmative vote of the whole number of its members and with the approval of the mayor, as a reward for conspicuously meritorious service, permanently retire from duty any member of the regular force or of the veteran reserve, after twenty years of continuous service in the department, upon certificate of the surgeon of the department or of a board of surgeons to be designated by such board or such committee, showing that such member is permanently disabled, physically or mentally, so as to be unfit for any police duty; provided such surgeon or board of surgeons shall further certify that, in his or their opinion, such disability is due either to the natural infirmities of old age or to injury received or exposure endured in the performance of duty in such department; and such member so retired shall be entitled to receive from said fund, during his lifetime, unless such vote is annulled by a unanimous vote of the members of such board or committee, with the approval of the mayor, a sum not exceeding five hundred dollars annually or, in case of officers other than patrolmen, not exceeding one-half the pay of such officers when retired, such sum to be payable in monthly installments. Such board or such committee may, by the affirmative vote of the whole number of its members, with the approval of the mayor, permanently retire any member of the supernumerary or regular police force who, while in the actual performance of police duty and by reason of the performance of such duty and without fault or misconduct on his part, has become permanently disabled, physically or mentally, so as to be entirely unfitted to perform such duty; and such member so retired shall be entitled to receive from said fund, during his lifetime, unless such vote is annulled by the unanimous vote of the members of such board or committee, with the approval of the mayor, an annual sum payable monthly, not exceeding one-half nor less than one-fourth of his previous compensation per annum; or, in the case of a member of the supernumerary force, not exceeding one-half nor less than one-fourth of the compensation of a patrolman of the regular force. Whenever such board or committee annuls a vote placing a policeman on the retired list, such board or committee shall file with the trustees of the reserve fund a written statement of the causes which determined them in annulling such vote. When any member of the police force has been killed while in the actual performance of duty or has died from the effects of any injury received while in the actual discharge of such duty, such board or committee may, by the affirmative vote of a majority of the whole number of its members, with the approval of the mayor, direct a sum not exceeding three hundred dollars a year, payable in installments, as such board or committee directs, to be paid from said fund to the widow of such policeman; or, if he has no widow, to his child or children not over eighteen years of age, and to his child or children being under eighteen years of age, after the death or marriage of his widow; provided such annual payment shall cease if such widow marries again, and shall cease when all of such children attain the age of eighteen years, and may at any time be stopped or the amount of the payment changed by the vote of a majority of the whole number of the members of such board or committee, with the approval of the mayor, and shall in no case be continued for a longer period than ten years.