Yeah, there is no way you should share your private key to anyone to make something like this. It really was simple and cheap to make.. Another user did this in a similar way in 2013 with print toner http://www.instructables.com/id/A-Stainless-Steel-Bitcoin-Wallet/.

Out of curiosity has anyone else had success with a different method? I think my method is very cheap but it's only the masking of the etching area that if delicate/most costly.

I've heard there are some commercial powders that can be bonded to metals with a laser. And a home method that  achieves the same with plaster of paris and isopropol alcohol. I'll give it a try the next rainy day in I get.