Nice find, I think you have an early date "dog tax license " tag. For whatever reason many Tennessee county dog licenses didn't have "dog tax" stamped on them, see examples below and other information from Dr William Bone's book: US DOG license tags
Rutherford............................... 1921, represents the oldest reported dog tax tag known to the author from Rutherford County.
Now, everyone drop off a few cans of pet food, make a small donation, or volunteer some time to their local no-kill animal shelter.
Wouldn't that be a nice tradition to start here on TNet, everytime someone digs up an old dog tag or license?