Governmental bodies approved by the board may sell any supplies owned by it after such supplies have become entirely unserviceable and can properly be classified as "junk", in accordance with procedures established by the Office of General Services. All sales of unserviceable supplies by the governmental body shall be made in public to the highest bidder, after advertising for fifteen days, and the funds from such sales shall be credited to the account of the governmental body owning and disposing of such unserviceable supplies.