A first lady’s diamond tiara will head “home” to Ohio soon. More than 300 donors have given the William McKinley Presidential Library & Museum in Canton, Ohio, amounts ranging from $10 to $5,000 in the last few weeks so that it can recover the piece from a pawnshop. The tiara had belonged to Ida Saxton McKinley, President McKinley’s wife, and then to descendants of Mrs. McKinley’s sister, Mary Barber. An episode of the reality series “Pawn Stars” that was broadcast in March showed a Barber descendant selling the piece to a star of the show, the Las Vegas pawnshop owner Rick Harrison, for $43,000.