Wordnet 3.0
NOUN (2)
1.
military identification tag worn on a chain around the neck;
2.
metal plate on a dog collar bearing its registration number;
WordNet (r) 3.0 (2006):
dog tag
n 1: military identification tag worn on a chain around the neck
2: metal plate on a dog collar bearing its registration number
Moby Thesaurus II by Grady Ward, 1.0:
19 Moby Thesaurus words for "dog tag":
ID card, badge, calligram, calling card, card, countermark,
countersign, credentials, identification, identification badge,
identification tag, initials, letter of introduction, monogram,
press card, serial number, signature, tessera, visiting card