Biafra stamps. "Republic of Biafra. May 30. 4D". (May 30, 1967, the independence of Biafra was declared.) Photo of a sheet of 9x9 identical stamps, received for free in Owerri after the war.
<bdi><a href="https://www.wikidata.org/wiki/Q42328204" class="extiw" title="d:Q42328204"><span title="Dutch history and art history teacher">Aart Rietveld</span></a>
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CC BY-SA 4.0
Aart Rietveld collection