If i'm correct, the hanko stands for 桑原、Kuwahara or Kuwabara.
I'm confident, at least, that you know more about this than I do. While the character I saw was what was given as the brush form of that seal script character, most obsolete characters are alternate forms of characters still in use.
And, as well, in the column of the K'ang Hsi dictionary which had the seal script character at the top, several modern characters were present. The one I chose seemed to most resemble the seal script character, and the seal script character was in the upper position on the margin - the character I picked being the first one - but the one you give is also present in that same column of the dictionary further down.
Of course, mulberries are very important in silk production, and the seal long predates the Beatles, so one can't be too disappointed that it isn't about
strawberry fields.