Betsy,

Unaccessioned materials (found in collections without a number) causes many,
usually unforeseen, problems.  First they may fall under the abandoned
property law(s) of your state, if you have any.  If so, they are certain steps
one must take in order to fulfill those laws so that your institution can then
gain legal title to the objects.  One must have legal title to whatever it is
in order to have the right to dispose of them.  This is just a very basic
intro. into the problems associated with unaccessioned/FIC/abandoned property
issues museum, etc. face quite often.  Basically your institution should make
an effort to contact the donor(s), if known, to see if they want the books
back.  If there are no legal steps to take, one should most definitely take
ethical steps in the disposal of these materials.  It not only reflects on how
your community will receive you, but it affects the whole museum, etc.
community on how these issues are handled.

I could go on and on, but I'll spare you and stop for now!  :)  Good luck!

Sincerely,
  Ginger M. Young, Registrar