Hi
You may already know but the story depicted on the tsuba is the "Plum tree of Amagasaki". The most popular version is that Yoshitsune ordered Benkei to write a notice for a plum tree he saw in Amagasaki which read, "Even in Kuan (a Chinese province noted for its plum trees) could not be found such a tree; ....... if a robber breaks a twig of it he shall forfeit one of fingers as a penalty". I've missed a bit of the notice but you can find the full text in Jolie's "Legend in Japanese Art" page 587. The notice makes a pun on branch and finger, both are 'isshi'.
I often find the the stories depicted on tsuba fascinating.
Keith