I use to work at a engine rebuilder who had tags made up and were hand stamped with a serial number, date, etc. then glued onto the block.
There are companies out there that custom make tags in many different materials for machines, electric motors, etc. Aluminum is real easy to stamp and will not rust. You can get brass, aluminum, stainless.
It would be the same for the Federal Lights Paul mentioned in another thread.
Any little tag can be reproduced easily.
They screen the graphics on the tags with whatever you want.
Odd shapes, if not a standard one they have, will cost extra to have the die made. There are 1000's of standard shapes from hearts to basic squares.
You just need 0-9 numbers and A-Z letters and a hammer to stamp the info in.
Darren