Abstract: A novel security seal which cannot be removed without destroying or defacing the seal, thereby rendering tampering detectable. The novel seal comprises a strap having a tongue end, a locking head at the other end, with a key and stop plate disposed therebetween. To engage the seal, the tongue is looped around and inserted through the locking head. As it is pulled tight, the key engages a lock plate inside the head. When the key is fully engaged, the stop plate abuts the head, preventing undetected tampering or withdrawal of the tongue. In locked position, the tongue remains exposed and is therefore a convenient location for coded information.