There is established within the Contingent Fund of the Senate a revolving fund which shall consist of (1) the unexpended balance of the appropriation “Contingent Expenses, Senate, Stationery, fiscal year 1957”, (2) any amounts hereafter appropriated for stationery allowances of the President of the Senate, and for stationery for use of officers of the Senate and the Conference of the Majority and the Conference of the Minority of the Senate, and (3) any undeposited amounts heretofore received, and any amounts hereafter received as proceeds of sales by the stationery room of the Senate. Any moneys in the fund shall be available until expended for use in the same manner and for the same purposes as funds heretofore appropriated to the Contingent Fund of the Senate for stationery, except that (1) the balance of any amount appropriated for stationery for use of committees and officers of the Senate which remains unexpended at the end of any fiscal year and (2) allowances which are not available for obligation due to vacancies or waiver of entitlement thereto, shall be withdrawn from the revolving fund. Disbursements from the fund shall be made upon vouchers approved by the Secretary of the Senate, or his designee.