Mass. Gen. Laws ch. 32, § 81: Amount of pension

Section 81. Any permanent member of a fire department retired under the preceding section shall receive an annual pension, payable weekly or monthly, equal to one half of the highest salary or other compensation received by him while he was holding the grade held by him at his retirement. The pension of any call or substitute call fireman retired under said section shall be the same as that of a permanent member of the first grade of the same department in which he served, or, if there be no grades, his compensation shall be that of a permanent member of the department performing duties like those which he performed.