Patty,

I have embarked on the quest which you queried about and have scanned many
of the early conchological works (Sowerby, Reeve, etc) and it is my
understanding that items produced before 1906 may be reproduced so long as
you own a copy of the original or are granted permission from the owner of
an original.  My presumption is that since many of the plates in these early
works were hand-colored they constitute a "work of art".  I guess that is
how so many Audubon "Birds of America" plates get reproduced.