There is established a working capital fund, to be available without fiscal year limitation, for expenses necessary for the maintenance and operation of (1) a central reproduction service; (2) a central visual exhibit service; (3) a central supply service for supplies and equipment for which adequate stocks may be maintained to meet in whole or in part the requirements of the Department; (4) a central tabulating service; (5) telephone, mail, and messenger services; (6) a central accounting and payroll service; and (7) a central laborers’ service: Provided, That any stocks of supplies and equipment on hand or on order shall be used to capitalize such fund: Provided further, That such fund shall be reimbursed in advance from funds available to bureaus, offices, and agencies for which such centralized services are performed at rates which will return in full all expenses of operation, including reserves for accrued annual leave and depreciation of equipment.