Introduced
In the historical account quoted by Citrus ID from Hodgson (1967), Nippon was described in 1931 and introduced in 1932. The same account reports that Eugene May made the Satsuma mandarin × Meiwa kumquat cross in Washington, D.C., but gives no year for the cross. These statements remain attributed historical accounts; they do not prove an origin chain for UCR's CRC 3360 accession.
Sources: [2]