I modeled this functional part and produced the mold used to make the wax patterns for investment casting. The mold halves for the main body were 3-D printed in stainless steel and mounted by the client in aluminum blocks for better cooling. The stainless steel printed parts took a lot of polishing for use in a mold. Epoxy based filler can also be used. The padding on the mating surfaces was machined off to provide a better seal. The other smaller parts were produced using lower temperature metal in rubber molds. The smaller patterns for the rubber molds were 3-D printed in bronze which is easier to polish but much more expensive per volume when printed at Shapeways. Another more expensive (but simpler!) production method for molds is to CNC machine them out of aluminum blocks. My client is an experienced traditional machinist.