Infrared is useful in some situations to detect overpainting on canvases but not appropriate here. If this is a fake, it's a much better job than we can do in the lab. Still, they agreed that one minor blemish on the surface looked like a fingerprint in lacquer. Determined to get a definitive answer, I gave permission to dissolve the finish in some inconspicuous spot. When I returned the next day, they were wreathed in smiles.
Nothing touches it.
Your shell has a natural surface, and that 'fingerprint' has got to be a natural defect. As a final clincher, they suggested putting the shell under ultraviolet light. I knew the result already. Most shells, including the valentia and 180 other species of cowries that I have tested, have no ultraviolet features. The two exceptions are the venusta cowrie from southwest Australia and the relatively common mappa , found throughout almost the entire Indo-Pacific.