Company Names, addresses, dates:
  Beck, Henry, Mineral water company, Alexandria VA (circa 1864) ¹
  Poggensee, Christian, Brewery, West end of King St, Alexandria VA (1865-1866) ²
  Pogensee & Beck, Alexandria VA

Notes:
An Alexandria Archeological report ² says that Christian Poggensee (c.1834-1903)³ teamed with George Steuernagel and opened a restaurant & brewery in Alexandria VA shortly after the civil war ended. Note that most references I found have Poggensee's name spelled with 2 g's, but the name embossed on the bottle below is spelled with only one 'g'.
An article in the Alexandria Gazette from Feb 27, 1864 said that the local bottlers were going to have to raise the price of their mineral water & cider to 50 cents per dozen (14) bottles, and it was signed by "FOGERTY & COLEMAN" and "HENRY BECK". I presume that those were 2 separate bottling companies, and that the "HENRY BECK" is the same "BECK" on the bottle below. I have no idea why it said "14" in parenthesis after the word dozen - was 14 really considered a dozen back then?
Anyway, I never found any city directory entries or newspaper articles that listed both Pogensee & Beck. Pogensee shows up in city directories in subsequent years (1870s on) as either a cigar manufacturer or a restaurant/saloon owner. The style of the bottle indicates it's pre-1880s; my guess is that Poggensee & Beck were together very briefly in the 1860s.

Bottles:

book # 530 This is an aqua 6.8" blob-top bottle marked: front: POGENSEE & BECK / ALEXANDRIA / VA bottle: BOTTLE / NOT SOLD (I painted the embossed letters with water-colors to make them stand-out)