A Backwoods Burial - Old Lestallum
First Available: Chapter 3
Other Requirements: Complete Swallowed By Shadows
Location: Old Lestallum
Rewards: 1,500 EXP & 10 Phoenix Downs
After you complete the Swallowed By Shadows quest from Dave at the Taelpar Rest Area you'll find him in Old Lestallum with another quest. Before leaving town you'll want to head into the Diner and 'Talk' with the owner there, a marker will be placed on your map for this quest narrowing down the location for you further. Once you've done that you can head on over to the quest location.
You'll find this Dog Tag right next to an abandoned shack in the center of the quest marker on your map, as shown in the screen shot below.