A customizable plastic frame meant as a form for making plaster or RTV molds for casting.
The two sides can be used by themselves to make a plaster blank which can be carved. The base can be used to hold modeling clay to directly make a RTV mold. A pre-formed sprue can also be added to the base for use with either plaster or RTV.
To make a plaster mold, print the sides and join them with rubber bands or electrical tape. Then place on a flat cookie sheet (modeling clay is useful to hold the forms in place) and fill with plaster. Then, after the plaster sets, you have a a nice flat surface to carve a pewter (or other mold) into.
To make a RTV mold, print the sides and base. Use modeling clay, wax, or any other modeling material to form your positive on the base. Join the sides and place over the base. Fill with RTV and wait for the RTV to cure.
Footnotes: I'm still tweaking this one. Drop me an email if you find a problem. I still need to test the base plate, sprue and labels with RTV and plaster, but they are based on experience with previous forms. Will test and post pictures soon.