"Car sealed means that the valve handle has been "locked" using a "seal." Today this would most commenly be a plastic strip but also old-fashioned wire and actual sealing wax can be used."
 
"CSO/CSC are different with LO/LC. The former uses wire and lead seal to limit operations to valve, people can break the seal in emergency situation. The latter uses chain and lock --- can't operate the valve until get the key."