Postal Shipment Safety Measure: safety measure that was carried out on a postal shipment
Seal: engraved hand stamp that was pressed into a soft sealing compound (e.g. wax or varnish) in order to securely seal a postal shipment on the back
Paper-backed Seal: seal placed between two layers of paper to securely seal a folded letter
Paper Seal: vignette with which a postal shipment is securely sealed on the back