I found a precise match of this wicker covered flask--same exact wicker, weave style and details, and same thick blown glass--listed by a Civil War expert, who also points to one in the Gettysburg Museum collection. While I can't say for sure this one saw battle, I am confident it is of the proper age, and know that these flasks were very popular with soldiers, as they were small enough to easily be conceal in a jacket pocket or haversack. It would originally have had four small wicker sling loops for a narrow cord--one can see on the sides, at shoulders and near the base, where these would have attached. Pretty cool.
While missing a stopper, it is in remarkably good condition--the wicker is tight and not very fragile--and if not filled again with whisky would make a very sweet little vase--maybe for a few daisies, or forget-me-nots! 4 3/4" tall x 2 3/4" wide x 1 3/8" deep.