The goat club I was a member of had a tatoo kit for members (one person would do the tatooing) it worked well, the small charge went towards club funds, that was some years ago.
I was talking to someone just a couple of days ago who tatooed one ear and tagged the other, they show goats.
one of mine has managed to break a tag so she only has the outside part, still fastened. Don't know where that leaves me legally?