One of the harder uniform items to ever find in original condition, this is a prime example of a field worn great coat / overcoat as issued to Union enlisted soldiers, mainly infantry, in 1861-1863. It is the early pattern known as a slash pocket front and retains the full cape as well as the back belt closure. It is missing a little fabric as shown and has some old field repairs, but is 99% original all the way and clearly shows use and even sweat stains around the collar area.
Unaltered greatcoats are far less common than those that have been altered, even re-dyed, for later use in the Indian Wars era. This would be an incredible addition to any Civil War uniform display!