Mark McGwire's 70th home run ball. A guitar once owned by Eric Clapton. A model of the Starship Enterprise.

These are among the items that an appraiser used in 2007 to establish the value of a collection of Lincoln documents and artifacts held by the Abraham Lincoln Presidential Library and Museum.

Appraiser Seth Kaller accepted the asking price of $23 million as the fair-market value of the collection sold by Louise Taper, a California collector, to the museum's private fundraising foundation, which is now raising money to retire the debt.

Kaller, who owns a business that acquires historic artifacts in New York state, wrote in his appraisal that he accepted the museum's claim that the items are authentic and that his assignment did not include authentication....