I think trying to remove the rust either physically or chemically risks removing the letters as well. Also, sealing the rust will preserve the patina of the piece. But start with light coats of sealer after testing in a less visible area, A thick coat can darken the color quite a bit. This might enhance the lettering or obscure it so better to proceed with caution. Also, you might consider adding a sheet of thick glass to make a top if the sealer doesn't do the trick. It would protect both the luggage and the lettering from each other.

The charm of this piece is its look and history. For your use, and to assuage your concerns, I'd just get a piece of glass for the top. How lucky you are to have this!

I agree that if you remove the rust than all printing will come with it. I like the glass idea. It may be a drag if you need to open the footlocker, but if you just want it as a stand, then I think it'll work nicely.

Thanks for your replies - sounds like leaving the rust is the consensus. The top has two ridges on it which would make glass difficult - I could put it between the ridges only or use some kind of spacer in each of the corners I guess - but I think the sealer might be the best solution. I do indeed feel lucky to have it.

The ridges don't look that high. I would make a template of the top, take a photo of the piece, and consult the place cutting the glass piece. This is less expensive than you would think. You can put clear stick on "bumper" pieces at the corners to keep it from being tippy. Measure the height of the ridges from the surface, and the glass company may have just the thing for the four corners. (I used to have a coffee table with this issue! Clear bumper dots saved the day.)