This portrait of McClellan appears in a scrapbook that sets Civil War officers beside a specimen of their handwriting.In this case the portrait is accompanied by a letter from McClellan, written many years after the war while he was Governor of New Jersey, in which he offers his support for what appears to be a widow's pension request:

The soldier's name appears to be "Doull," and there was indeed a single Major Doull serving in the Union Army. Doull seemed to have performed some reconnaissance preserved in this map.

View the original post at the Notes for Bibliophiles blog.