This was found recently from the secret vaults of the Ishikawa family, and was determined to be the original handwriting of Sadanobu because of his autograph of 'Sadanobu started writing this from one o'clock to three and finished from three to five on the same day' (同日未刻染筆申時終切定信) in the postscript.
近来、石川家の秘庫から出たもので、その奥書きに「同日未刻染筆申時終切定信」の自署があるので、定信の真跡と決定された。