"Dog tag" is an informal but common term for the type of identification tag worn by military personnel. The tags are primarily used for the identification of dead and wounded soldiers; they have personal information about the soldiers and convey essential basic medical information, such as blood type and history of inoculations. The tags often indicate religious preference as well. Dog tags are usually fabricated from a corrosion-resistant metal. They commonly contain two copies of the information, either in the form of a single tag that can be broken in half or two identical tags on the same chain. This duplication allows one tag (or half-tag) to be collected from a soldier's body for notification and the second to remain with the corpse when battle conditions prevent it from being immediately recovered. The term "dog tags" arose because of their resemblance to animal registration tags.