This nifty, large, unfranked Official Business cover(now empty) of the U.S. Treasury Department, Second Auditor's Office, was sent from Auburn, New York, to J. H. Thompson, M.D., Surgeon, 124th New York Volunteers, Goshen, New York, on April 16, 1865! An E.B. French, was the auditor in charge of the matter concerned. Interestingly, John Hudson Thompson was court-martialed for supposed, "cowardice," and "disloyalty." Here's an interesting link to an article about his story: https://www.americanheritage.com/surgeon-thompsons-separate-peace
While Surgeon Thompson was not found guilty of disloyalty, he was found guilty on 6, other counts, and cashiered from the Union Army, with the loss of all pay and allowances. He was discharged on November 25, 1864, having made no appeal to verdict rendered against him. He went home to Goshen, New York, but was later given a pardon by President Lincoln after a number of other officers of the 124th News York Volunteers, and the U.S. Secretary of State, William Seward, appealed to him on Surgeon Thompson's behalf. His civil rights were thus restored, and the lost pay and allowances eventually paid to him(I believe that the cover in question could very well have to do with the restoration of that pay and those allowances.). He was eventually even offered a chance to re-enlist, but didn't pursue it.
To continue, the CDS cancel from the Auburn Post Office is pretty good, but not complete, due to how the envelope was opened(and reduced) at the right side. There is a neat, auxiliary notation asking the postmaster(s) involved to forward the mail if necessary!
Lastly, outside of some glue stains on the back(the cover was likely put into an album at some point in the past), and some stains around the bottom, and left corner of the front, the envelope is in pretty good shape for something that's around 159-160 years old! The back flap is 95% intact. There are some minor creases here and there. Noted blemishes aside, this O.B. mail from the U.S. Treasury Department to J. H. Thompson, Surgeon, 124th New York Volunteers, is still really neat!