Step 1: Get the Tin and Remove the Paint
In the end I didn't do any of this. I have access to a small sandblaster and it made quick work of it. It left the box with a nice matte finish. I realize that few people with have this kind of tool around, so you'll just have to do your best.
It is also possible to just paint over the whole thing. I would still sand it mostly to help with paint adheasion. Painting it would probably be best done later after the next few steps.
Step 2: Cut a Window in the Lid
File the edges with a fine needle file or diamond hone. Remove the burrs as best you can without bleeding too much.
Step 3: Surface Finish
Step 4: Glue in the Window and Line the Box
Glue the window in with a hot glue gun or RTV. I prefer RTV, but it takes a while to dry and it can get all over everything. If you get glue on the window while installing it, don't try to clean it up. Wait for it to dry and polish it clean and clear with a plastic polish compound. Or put a new one in and be more careful.
Finally, line the box with felt or a nice handmade paper. You can also stick an adheasive magnet for business cards to the back of the box.
That's all! Whatever you put in the box will need some kind of mounting. Poster Putty works well and magnets stick to the box great.
My blog: Ossa Piscium