A dog tag is a form of identification worn around the necks of soldiers at war. It consists of an aluminum pendant on a sturdy ball-and-socket style chain. The pendant is embossed with various information, such as name, date of birth, blood type, branch of service, and relevant medical information.
The all of the edges of the pendant are curled over to make a narrow frame around it. This smooths any sharp edges and strengthens the object. The there is a notch at the short end opposite the connection to the chain. This notch reputedly facilitates the embedding of the tag between the teeth of a dead soldier prior to transport.