What's a sentai?
Sentai
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Series 100 year histories from Meiji Era, Ministry of the Navy, printed by Hara Shobō (Japan)
Vol. 173, Histories of Naval organizations #3 (1), original plot in 1939, reprint in May 1971
Vol. 174, Histories of Naval organizations #3 (2), original plot in 1939, reprint in July 1971