Hmm... well, at the risk of giving away proprietary trade secrets...
I start with a drawing...
and I go to the 3D printing service "Shapeways:"
https://www.shapeways.com/creator/2dto3d#landing
and I upload my drawing. After a few steps I get a preview of the stamps, which might look like this:
I chose a material (in this case, the cheapest plastic). They do various checks of how thick it will be, and... eventually I pay them, they print it, and they send it to me.
I do something similar with the head badge, except it was "printed" in brass or bronze. That actually means they print in castable wax and then turn it into metal by a lost wax casting process. It comes to me flat; I file it as needed, add paint, sand the paint of the high parts, curve it to fit a bicycle, and... that's about it. Please don't tell anyone.
I made [MENTION=381793]gugie[/MENTION] four head badges; two of them are brass, two are bronze. I can't tell the difference, but I believe they will oxidize differently, so in a year or two they should be different colors.