1833 May 11:
North Windham post office opened. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)
1935 July 11:
The circular postmark is approximately 32 mm in diameter. The four horizontal bars to the right of the circle are approximately 6 mm on center.
(click on image to enlarge)
1985 September 28:
North Windham post office closed. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)
South Windham
1828 March 11:
South Windham post office opened. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)
date?:
South Windham post office.
(click on image to enlarge)
1934 June 8:
The circular postmark is approximately 29 mm in diameter.
(click on image to enlarge)
1938 August 27 through 1950 September 29:
The circular postmark is approximately 30 mm in diameter. Note that the 1938 of the first cover is upside down.
(click on an image to enlarge)
1985 September 28:
South Windham post office closed. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)
Windham (1)
1800 September 5:
Windham (1) post office opened. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)
1838 July 24
Manuscript postmark. (notation; letter)
(click on image to enlarge)
1872 August 30:
Windham (1) post office was renamed as Windham Center (2) post office. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)
Windham Center (2)
1872 August 30:
Windham Center (2) post office opened. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)
1889 March 12 through 1889 June 12:
The circular postmark is approximately 32 mm in diameter.
(click on an image to enlarge)
1891 November 23
It appears that the postmark was originally circular but later became distorted.
(click on image to enlarge)
1906 April 14:
Windham Center (2) post office closed. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide)