After reading the 2 pages posted by Dutch Blacky, I wonder if the original mold was made out of wood, then sand cast and a pour of either cast iron or maybe even brass. Then a second sand cast of the inside of the second half of the 2 molds. 2 wood molds that would fit inside of each other would be easier to carve, and cast than using an iron ingot and working it to a mold shape.