Gentlemen,  One other aspect of donating a valuable literature
collection to some so called preservation organization is this,
and it happened to me.

Donate your items, be given emphatic assurances that they will remain
in the collection and be available for future researchers, and then see
them auctioned off a couple of years later so the organization can pay
their property taxes or the light bill.  Or the organization goes under
when the principal founder dies, and the whole thing is auctioned off
and dispersed.

Selling on eBay, or some other site, only jacks the prices for such
items up to the point where the serious researcher just cannot afford
to obtain them.  Look at the prices paid for such literature, or for
the instruments themselves -- pure gouging.

Jim Crank