Layla's Dog Tag

Real Life
"Dog Tag" is an informal but common term for a specific type of identification tag, usually worn by military personnel. The tags' primary use is for the identification of dead and wounded soldiers; as such, they have personal information about the soldiers written on them, and convey essential basic medical information such as the soldier's blood type and history of inoculations. They 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 as two identical tags on the same chain. This purposeful duplication allows one tag, or half-tag, to be collected from a soldier's dead body for notification, while the duplicate remains with the corpse if the conditions of battle prevent it from being immediately recovered. The term arose and became popular because of the tags' resemblance to animal registration tags.

Avenger
In the series, Layla held onto a tag with her name on it since childhood.

In the denouement of the last episode, Layla walks alone while holding onto her tag. Then she vanishes. Her tag is last seen hanging from a cross. It can be deduced that the tag was found and later placed on the cross by Nei.

Trivia

 * In another animated series by Bee Train, Madlax, the titular character carries a pair of dog tags that barely spell out her father's name on them.