Thanks for your words, Patrice and Johana. It is very easy with an old metalturner machine (I don't know other name), I am leathercrafter, woodcrafter and metalcrafter. The machine is connect to a computer, I get the pic that I like and the metalturner machine engraves the work in a sheet or in a plank made of the alloy of steel and alluminium in a hour or less. After I turner the hole or tube in the back for handle. Finish the work polishing at hand.
For the steel stamps is more difficult. The machine engraves the design in the steel stick and after the stamps must be templated for get hardness with hot in an oven and after cool down faster in water or oil and finishing the work polishing with a metal file. Is like make a knife.
I can made anything design with a computer and this machine, I only need the pic in jpg or gif files and putt the final touches to the project. The limit is in the size, 1" x 1", or a little bit more, but is better a lower size. The steel and alluminium alloy sheet is not cheap if I made only one or two stamps. The celtic circle have a cost of 40 € ($53) making only one. I am thinking made 100 of every design for get it more inexpensive.
Let me show here other stamps in stainless steel and in steel blued finish.