The paternity of Abraham Lincoln; was he the son of Thomas Lincoln? An essay on the chastity of Nancy Hanks by William E. Barton. (OCLC #882677)
The form of Lincoln’s heading on the bottom card is the current one; the form on the top card has already been modified once by hand, but not quite to the current form – the original form on the top card is not even in the current authority record. It does have a link to a similar heading, United States. President (1861-1865 : Lincoln) describing that role, though it is not for use as a subject.
Maintaining consistent name authority is much easier and less error-prone with a modern ILS. Always control your headings in OCLC when you can to help this process!