Was thinking about similar, already mentioned on the forum, but it's a bit different.
I was using the same kind of metal business card, but I would like to engrave the letters into it with a hand engraver tool. My initial thought was to punch in the letters like a dog tag, but there's not enough place to punch all the letters, because of the blending of the material, you can't condense the characters enough to fit. So I have already ordered the metal cards off from ebay, now I'm searching for a proper hand engraver.