I have examined a retouched Cypraea sakurai. It was a real but faded
specimen on which someone had redrawn the pattern and then somehow reglazed
the shell.  My first reaction on seeing the specimen was that it was the
best specimen of the species I had ever seen. Under a microscope however, I
could see that the pattern had been drawn on with brown ink. In a real
cowrie, the pattern is laid down in three dimensions, and is slightly cloudy
under magnification. In the retouch specimen, the pigment was applied along
a single surface rather than built up in three dimensions.  The glaze of the
surface was also too perfect.  In a real specimen, the growth lines of the
shell give a slightly wavy reflection of light, but in the retouched one,
lights were reflected too exactly.  The fake is certainly worth the price,
and I wouldn't try to test it with solvents if you can tell by microscopic
inspection that it is fake.
 
Gary
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Gary Rosenberg, Ph.D.                     [log in to unmask]
Malacology & Invertebrate Paleontology    gopher://erato.acnatsci.org
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