Oban probably first printed in 1979, commissioned by Osaka Mainichi for the Narazaki catalogue raisonne. Even though must be carved before 1964 there is no evidence of print being published earlier. The Watanabe family seal is copyright to Watanabe Tadasu.
A few prints had Watanabe's red personal seal, presumably applied by Watanabe Tadasu, and the last time seal known to have been applied.