There was a census done in Philadelphia (1870?)that was so full of errors the Census Bureau ordered that it be redone. The census taker job was a political hand out in most places during the 1800's. The only requirement was reading and writing, which in 1850 was not a common skill set.

Here is Nathaniel N Wilmot listed as a gunsmith, 1864 in St Paul
View - St Paul City Directory 1864

Here is N.N. Wilmot listed as a gunsmith, 1865 in St Louis
View - St Louis City Directory 1865

Pete