I had this idea of using a cupcake pan to make ingots. I figured out that I can use steel stamps to identify the mold by stamping the bottom of the pan. I stamp from the bottom so the impression is backward inside the pan. I had to pour my first ingot, then used it to support the inside of the pan so that it wouldn't collapse when I hit the stamp with a hammer. A cupcake of lead is a little over 2 pounds so I stamped it "2 lb", and the type of lead used. For example I've been melting range lead recently so I stamped it "bullet lead", but since I have a bucket of wheel weights coming to me in the near future, I'll just stamp another cupcake "wheel weight". This way I'll alway know what kind of lead I'm using. I bet everyone has an old nasty looking pan crammed away somewhere in the kitchen, I bought a new one for food and used the old one for lead. With twelve cupcakes per pan you have the ability to identify several different alloys. I have a small melting pot so I only needed to stamp two of them for the bullet lead alloy, when I get the wheel weights I'll stamp two more.
Here's a pic of the bottom of the pan.
And here's a pic of the lead ingots.