Perhaps in speaking of "fake" shells we should differentiate between out-and-out manufactured specimens (a Cypraea leucodon or Cypraea valentia created by reworking a Cypraea mappa or Cypraea tigris) and a "retouched" shell, which actually is the species it is represented to be, but has had its pattern and gloss restored. Either type of fake can be identified as fake by a dip in a non water-soluble organic solvent like xylene, toluene, chloroform, etc. Paint thinner will also work. These solvents quickly attack the paints and resins used in such restorations, but won't hurt an actual shell. Of course, this approach is not advisable if you want to keep the fake looking as it does! These solvents will not just identify a fake, they will also "ruin" it. Some water-soluble solvents, particularly acetone, will also expose fakes, but I shy away from using them on shells. They are extremely drying, and may have a deliterious effect on some pigments which are naturally hydrated. Paul M.