Hey Whit,
there are several ways that these could be done. With modern technology press dies could be made with lasers, CNC routers/machining centers, molded/cast, etc. It would come down to economics, and how long the dies are expected to last.
In the old days a wooden master pattern would be made, then it was used to make the mold which was then cast. The casting would take some polishing to be ready to use. Another way would be for a tool, and die maker to basically carve it out of a chunk of metal. Castings would usually be for mass production , the tool maker approach would be for precision, as it is a very expensive way to do it.
Today a design can be input into a CAD/CAM computer program the sent to a CNC machining center, laser, router, etc. They still require a little dressing up, but a ton of labor is saved.
There are folks on the forum here that can do this die making for you. Some dies are done in Delrin which is a very stiff, hard plastic that works very nicely.