From the shape I would say it may also be a mustard pot.

Hi,
the piece that you have is ‘Nippon’ Porcelain and was produced in Japan during the first half of the 19th Century and carries the “Crown (Square) Hand Painted Nippon Mark”, which is found in green and green with red. No known manufacturing date(s) are known. (Van Patten’s #10)

Unfortunately, due to the wear and condition it would be of no commercial value and it may be better to keep it as an heirloom to pass down in the family.

Best wishes
Andrew Jackson
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