Section 80. In cities, except Boston, which have accepted this section or corresponding provisions of earlier laws by vote of the city council, the appropriate retirement board, established under section twenty, shall retire from active service and place upon the pension roll any fireman, call fireman or substitute call fireman of the city whom the city physician certifies in writing to be permanently disabled, mentally or physically, by injuries sustained or illness incurred through no fault of his own in the actual performance of duty, from further performing duty as such member; or any permanent member of said department who has performed faithful service therein for not less than twenty-five years as such or as a call member and permanent member of said department, if in the judgment of said board such member is disabled for useful service in the department; provided, that any permanent member of said department who has performed faithful service therein for twenty-five years as aforesaid shall, at any time after attaining the age of sixty and before attaining the age of seventy, be retired at his request and shall, on attaining the age of seventy, be retired without any request on his part, and no other permanent member of said department shall remain in service after he has attained or shall attain the age of seventy. Any acceptance of this and the following section may be limited by the vote of acceptance to any one or more of the classes of firemen hereinbefore set forth.

No fireman whose employment begins after June thirtieth, nineteen hundred and thirty-seven, shall be subject to the provisions of this section.