Last known picture of Abraham Lincoln

[STS Lincolnite]

Didn't Nicolay and Hay in one of their books state that the last photos of Lincoln were taken in March, 1865? I don't have any copies so I can't check. That doesn't illuminate us on how or why the Gardner photo was previously dated April 10, but it would narrow the time of Gardner's session to before early March. This would then be consistent with the February 1865 dating.