The members of the board shall be trustees of the fund, and shall have exclusive management of the fund with full power to invest the moneys therein subject to the terms, conditions, limitations and restrictions imposed by law upon fiduciaries. Subject to like terms, conditions, limitations and restrictions, the trustees shall have power to hold, purchase, sell, assign, transfer or dispose of any of the securities and investments in the funds, as well as the proceeds of investments and of the moneys belonging to the fund.

The board shall annually allow regular interest on the mean amount for the preceding year to the credit of each of the accounts. The amount so allowed shall be credited to each contributor's account.