1832 August 2:
Pembroke post office opened. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide.)
1906 September 24:
The circular postmark is 29–30 mm in diameter.
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1935 September 23:
The circular postmark is 32–34 mm in diameter. The four bars to the right of the circle are approximately 6 mm on center.
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2020:
Pembroke post office. U. S. Route 1; Pembroke, Maine 04666. Lat./Long.: N 44°56′58″ x W 67°10′41″
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today:
Pembroke post office is still in operation.