The following may shed some like on the above thread.
 
The following tale of the rice-paper Wentletrap is told by S. Peter Dance
in his Rare Shells, 1969 (p. 87):
 
"Another story, constantly repeated but never substantiated, tells of
clever rice-paper forgeries marketed during the nineteenth century by the
Chinese for sale to unsuspecting collectors unable to purchase the genuine
article. The fraud was detected, so it is said, by the owners who dipped
the 'shells' into water to clean them, when Precious Wentletrap became a
worthless blob. If counterfeits really did exist at one time it would
appear that they have all been reduced to pulp long ago - nearly all, that
is. On that has excaped dissolution is owned by a London shell dealer. It
would deceive an expert, for apart from its lighter weight and duller
surface-texture there is nothing to suggest forgery; and successive owners
have detached tiny pieces to see if they disso;ved in water - and they did.
Such drastic action is unlikely to be repeated; its owner treasures it too
highly for that."
 
Later Dance wrote in A History of Shell Collecting, second ed., 1986 (page
43, and p. 43, footnote 7) the author states:
 
"Stories always accrue round highly desirable objects and 'la Scalata' was
no exeption. The most persistent of these maintained that the Chinese used
to make rice-paper forgeries for sale to unsuspecting collectors who could
not obtain the genuine article. It is a story which has yet to be
substantiated."
 
Footnote: "Some reviewers of the first edition of this book took me to task
for not retailing the story. In 1969, in my Rare Shells, I went to the
opposite extreme and wrote about a so-called rice-paste specimen I had seen
in the collection of a London shell dealer. Many years later I examined
that specimen again and concluded that I had deceived myself. The story of
the rice-paper forgeries of the Precious Wentletrap, alas, would appear to
be apocryphal and I shall not burn my fingers over it again. But I have
every confidence that others will continue to do so!"
 
As far as I know this was the last word on the subject. I would love to
hear otherwise.
 
Stephen E. Pober