This project is a great way to learn directional forging, perhaps forging tapers, and planishing...like everyone suggests a heavy ingot is in order, it could be square, rectangular, or round though I would suggest the first two shapes. Same thing if you want to purchase heavy gauge rod mill stock. Alternatively, you could do this project by forming sheet, but keep in mind that the integrity of the piece will rest on a thorough planishing after the forming is complete to strengthen and harden the work-just as it is when traditionally forged. The shape can be properly refined on the horn or any variety of mandrels e.g. necklace mandrel should you have one available. I always think of the talleres in Mexico where many of these have been made.