It’s an anachronism of the sword’s description because the sword is meant to describe the author. I’m guessing that mickey mouse holds some significants to The Silent Storm. Or perhaps they just like the juxtaposition of Mikey Mouse on a sword.
Or if you look at it from a straight storyworld view, it means that the sword has either traveled through time, or through alternate dimensions. Depending on how sci-fi or fantasy you want to get.
Anyways, I like what the sword says about you, and I enjoyed the story. (Though I have to agree that the bolding is a bit over the top.)