SECTION 1. (a) A retired member of the state employee or the State Teachers Retirement System or a teacher retired from the State Retirement System of Boston who has been retired under the provisions of this chapter or similar provision of earlier law on a superannuation, accidental disability or ordinary disability retirement allowance prior to January 1, 1990 shall have a one time supplemental adjustment to his/her retirement allowance. Said one time pension adjustment shall be calculated by multiplying the full years of service credit at the date of retirement by the number of full years such member had been retired and multiplied by a factor of two. This one time adjustment shall occur no earlier than January 1, nor later than January 31 following the passage of this Act. The sum of the dollar amount of such one time pension adjustment, together with the amount of retirement allowance to which the adjustment is applied shall become the fixed retirement allowance, for all future purposes including the application of subsequent cost of living adjustments in future years.

 (b) Any system other than the State Employees¹ Retirement System and the Teachers¹ Retirement System may, by accepting the provisions of this section as hereinafter provided, elect to provide this one-time supplemental adjustment pursuant to this section by majority vote of the legislative body. For the purposes of this section, legislative body shall mean in the case of a city the city council in accordance with its charter, in the case of a town the town meeting, in the case of a county the county retirement board advisory council, in the case of a district the district members, and in the case of an authority the governing body. Acceptance of this section shall be deemed to have occurred upon the filing of certification of such votes with the commission. A decision to accept the provisions of this section may not be revoked.