I scanned a real shell using a Steinbichler Comet white-light scanner. 3D scanners of this type are high-precision instruments mostly used in laboratory and factory environments because of their cost and sensitivity to vibration, dust and temperature.
Dozens of scans were combined and blended together to create a 3D representation accurate to less than a thousandth of an inch. Hanging loops were sculpted in a style similar to the shell, creating a consistent look. The silver casting shows no printing lines, and even the sprue locations have been polished and sculpted by the silversmith to blend into the design.