George: firstly, thanks for the reply. To be honest with you, the thought of maybe putting a knob on top never really occurred to me. In my mind I always had the image of having precisely this finial on top. And obviously, if you can't see it, you won't make it, so I didn't. I'll keep it in mind, though.
Brian: again, thanks for the comment. I have to admit that my freehand turning of spheres is not great. Something I either need to practice or buy (or make) myself a sphere turning jig. Yes, the lid is a little flat, and so is the bottom of the box. I personally think a flat top to the lid would not work well. But there we really get into the field of personal preferences.