It would be better to have the coin in hand, but I tend to agree that it's not a proof. In this time, Japan's modernization drive had resulted in the purchase of up to date mint machinery (they were later on-sold to China, where they remained in service for many more years.) They might have set the weight of the strike too heavy, sacrificing speed for quality. This will produce nice, sharp coins, sometimes even with partial frosting effects. However, since the planchets were not polished before striking, they would not count as proofs. See also
this thread.
Peter
