PrettySmallThings@AppleF you might check the Shapeways forums - there are occasionally discussions about the suitability of various materials for investment casts. I unfortunately, don't have experience with the process.
PrettySmallThings@AppleF You can read more about the plating process on Shapeways' material page, but here's an excerpt: "Precious Plated Metal models are fabricated using a complex seven-step process. First, the model is printed in wax using a specialized high-resolution 3D Printer. It is then put in a container where liquid plaster is poured in around it. Once the plaster sets, the wax is melted out in a furnace, and the remaining plaster becomes the mold.
Molten brass is poured into this mold and set to harden. The plaster is broken away, and your product is carefully cleaned and hand polished. Each product goes through two plating steps - first a layer of palladium is applied to provide strength and durability. Then your selected precious metal plating provides the finishing touch."
The two product photos shown are: Frosted Ultra Detail, which is perfect if you want to paint and decorate a miniature of your own, or Polished Brass (not plated.)