Up for sale is an Antique Civil War Era Soldier's Violin/Fiddle Hard Case. This case would have originally fit a Full Size 4/4 Fiddle.
It is also marked U. On the case which leads me to believe that it was most likely government issued.
I've never seen another like it. As you can see in the pictures, it is obviously worn and has wear consistent with age. The case measures 31 long.