Hello chrisd,

The engraving and texturing maps can be created from various bitmap and vector formats, they don't need to be NURBs. I believe you can also use scan data as well. I'd investigate having the items modeled to within a manageable tolerance, have the molds milled conventionally, then have the NURBs data, maps and/or scan data sent along with the molds so the detail can be mapped accurately to your molds. The molds are then engraved by subtracting a relatively small amount of material for the finish and detail you desire. I know you can accomplish this chemically, through EDM and laser ablation.