Here is how to make the stamped tag.
1) place your metal tag on a rock hard surface like concrete. Make sure that if it is on concrete you put some kind of paper behind it or the concrete will create imprints on the back.
Having even a wood surface didn't put the letters through well.
2) put the stamp in the correct spot on the metal. If you are spelling something make sure you start with the middle letter or symbol.
3) Use a hammer to pound the letter in. Make sure that the letter NEVER moves, even a little will cause the letters to look off.
It's hard to determine how many hits you need to hit with the hammer. I know some letters you need to hit it less (like 'I' and 'T') but some metals and thicker or thinner and it is hard to determine.