Found this bottle near a farm house built in 1850. Also Union Army camp site. I don't think it is that old as it does have a seam. On the bottom are letters and numbers: X721 (on top), 3 (in center), 10 (below 3). Just below the rim is printed 2 1/2 oz. It may be completely modern. I just don't know. Any ideas as to it's purpose and age would be appreciated.