Car seal comes from the rail car and freight industry. Once rail cars were filled, an inspector placed a metal wire on the loading valves. If the wire seal was broken, then the shipment could be refused. Each seal had a serial number or an imprint of the inspectors company. In the chemical industry it is an administrative control system to assure valves are not used inappropriately. For example, valves under relief valves are sealed open. This is better than chains and locks that used to be used in plants. If the valve is accessable by the public, like pipelines, then chains and locks are still used.