aquachigger ~
Cool bottle. Most bottles can usually be dated by determining what type of closure/finish/lip it has. In the case of your particular bottle, it appears to have a "Tapered Collar." Below is an example of one and some additional information. If the finish is correct, I'd say it qualifies from the Civil War era, and possibly even earlier.
SBB
[ Copy/Pasted Text ]
TAPERED COLLAR - Also called a sloped collar, long tapered collar, and likely other names. McKearin & Wilson (1978) described this finish style as a "plain broad sloping collar."
The tapered collar is an early, one-part finish that is usually moderate in height (1"), wider at the base of the finish than it is in vertical height, and flares distinctly out from the rim to the base of the finish. It is similar to the oil finish except proportionally shorter, i.e., the oil finish is usually taller than it is wide at the base. It also shares some physical similarities - as well as use on some similar types of bottles - with the blob finish except that finish is rounded on the outside surface whereas the tapered collar is flattened. It is also similar to the upper, taller portion of some mineral finishes.
This finish is probably most often seen on soda/mineral water and beer/ale bottles made in the 1840s and 1850s, largely giving way to the blob finish in the early 1860s It is also seen frequently on some medicine and bitters bottles, a few figured flasks and liquor bottles from the same time period stretching through the 1860s.
The applied tapered finish pictured below is on an early mineral water bottle that dates from the late 1840s, which was made by the Dyottville Glass Works of Philadelphia, PA.