Notwithstanding the foregoing, whenever the managing board of a local retirement fund includes municipal employees who are not elected by the people and who are not members of the board of education, nor employed or appointed by the board of education, the managing board shall pay monthly to each retired teacher, in addition to whatever retirement income such retired teacher is otherwise entitled to receive from the local retirement fund, an amount not less than such retired teacher's proportionate part of the excess of the total of the state annuities received by the managing board for all retired teachers for that month over that for the corresponding month of 1961.