1792 June 30:
Brunswick post office opened. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide.)
1851 October 23: [year determined from contents] (notation; letter)
  The circular postmark is approximately 32 mm in diameter.
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1852:
Postmaster: John McKeen (source: Maine Register and State Reference Book. 1852.)
1859 April 30:
  The circular postmark is 32–33 mm in diameter. Note: this cover was mailed to the mother of Joshua L. Chamberlain, who later became a general of note during the Civil War.
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year? July 12:
  The circular postmark is 24–25 mm in diameter.
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year? January 8:
  The circular postmark is approximately 26 mm in diameter.
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1890 April: [This cover is backstamped 1890 April 2]
  The circular postmark is 26–27 mm in diameter.
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1892 December 19:
  The circular postmark is 28–29 mm in diameter.
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1896 November 5:
  The circular postmark is 24–25 mm in diameter.
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1907 March 29:
  The circular postmark is 23–24 mm in diameter. The vertical bars to the right of the circle are approximately 4.5 mm apart on center.
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1911 January 12:
  The circular postmark is 29–30 mm in diameter.
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date?:
  Brunswick post office.
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1949 October 9 through 1949 December 29:
  The circular postmark is 29–30 mm in diameter.
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1939 October 7 through 1950 July 12:
  The circular postmark is 20–21 mm in diameter.
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2019 May 20:
  The postmark, which was applied at the Town Hall, is 63 mm high and 70 mm wide.
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2021:
  Brunswick post office. 30 Pleasat Street; Brunswick, Maine 04011. Lat./Long.: N 43°53′50″ x W 69°58′04″.
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today:
  Brunswick post office is still in operation.
Merepoint
1895 May 11:
Merepoint post office opened. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide.)
1913 July 2:
  The circular postmark is approximately 31 mm in diameter. The horizontal bars to the right of the circle are a little more than 4 mm on center.
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1967 May 19:
Merepoint post office closed. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide.)