Paul Romaine's thoughtful posting about library security
made me wonder if there isn't a middle ground:
could not these rare materials be scanned or microfiched
for use in research related to content (e.g., checking a citation),
so that the materials would not need to be handled
except for research which related to the physical object.
I don't know, but it would seem that this would considerably
reduce the numbers of people handling these collections physically,
and thus make tighter security easier and more efficient when
the actual object needs to be handled by the researcher.