"Sec. 9-A. The Board of Directors shall also have the power and authority:
"(a) To create, establish and operate a "Self-Insurance System" in order to offset possible damage or loss of cash-in-transit that the Bank may suffer on account of cash and check remittances to its branches and agencies and vice-versa;
"(b) To create and establish a "Provident Fund" which shall consist of contributions made both by the Bank and its officers or employees to a common fund for the payment of benefits to such officer or employee or his heirs under such terms and conditions as its Board of Directors may fix;
"(c) To create and establish a "Supplementary Retirement Plan" for qualified officials and employees for the payment of a gratuity equivalent to one month salary for every year of service rendered by them but not exceeding two (2) years in the aggregate;
"(d) In its discretion, to accept assignments of, or as payments, certificates of indebtedness of the Government or other such similar securities: Provided, however, That the authority herein granted shall not be used as regards backpay certificates."