Thanks, James, for raising this important topic.  Publicity in this way
might just help matters...

I think things ARE improving, gradually.  Dealers perhaps didn't realise
the importance of good data 10 years ago, but they certainly do now.  I
know that I've been able to persuade my own collectors to give me much
better data than they were doing 3 or 4 years ago.  But shells being
recycled from old collections are always going to crop up with weak or
"dubious" data.

To be fair to shell dealers, we do often have to hide the collector's
name purely to protect our own livelihoods.  Collectors in Third World
countries may be unwilling to give detailed locality data because they
rely solely on those sources for their own livelihoods.  Not an ideal
situation, true, but it's understandable.

From my own experience, dealers also need to beware of the dilemma of
"being told what you want to hear", when asking a native collector for
accurate data.  The classic instance is being told that something is
from "very deep water", when the collector believes that this makes a
shell more desirable.  It might be a very rare and desirable shell from
SHALLOW water.

My two pence' worth...