5. If, after publishing such notification, such thing is unclaimed, or if the person claiming the same fails to pay the amount due for the said expenses and any customs-duties or other charges properly incurred by the Government in respect thereof, the Government may sell such thing by public auction, if it is of a perishable nature, forthwith, and, if it is not of a perishable nature, at any time not less than six months after publishing such notification as aforesaid.