Here is a pre-owned VINTAGE Hewlett Packard 21 Calculator.  PLEASE READ - This Calculator seems to not work correctly.  Batteries were inserted and numbers were punched ( see picture showing numbers appear on calculator ).  Battery Connector on inside has come unattached but works when batteries are inserted correctly.  Battery Door does not stay closed so tape will need to be used to keep door shut.  This Calculator is being sold for parts or repair only - NO RETURNS !  FREE SHIPPING in the Continental United States ONLY !!