Chattanooga Tenn Stampless Cover

Any thoughts on this?

Well known union occupation/military cancel from Chattanooga. Unusual to see it on stampless mail (in my experience). James Cate has a really nice exhibit of these markings and wrote an article on them that appears in the 2016 Congress Book, which I unfortunately do not have in front of me.

Probably 1864 use given the January date. Due 3 allowed for collection of postage on delivery, which was typical for union soldier's mail. There is a soldier's letter endorsement at left in pencil (at a glance, it does not appear to be technically correct, since the endorsement was supposed to both identify a unit and bear the signature of an officer of that unit)