Hi Richard, I also have a Franklin Mint piece it's an efu Tachi supposedly a copy of the one that was presented by the emperor to Minamoto no Yoritomo, I believe the blade is chrome plated so any scratches will most probably be there to stay, if someone offered me £1000 for it I would have no hesitation, I bought it for £75 some years ago and only keep it because it looks pretty and the only piece that I allow the "sages" to run their thumbs across the blade then declare how sharp it is, also it's the only "efu tachi" I will ever get my mitts on. The one you have is I believe named "the Sword of the Samurai" by franklin mint, the stands that they come with are the best part of them, initially why I bought mine.
Thinking about it you could try Autosol which you can get from any car accessory shop and is a chromium polish.
A point to remember is that the likes of franklin mint creations are not Nihonto although many sellers would want you to believe they are just to sell them.
Bernie