Bernard and Chris - thank you so much for your information and your thoughts. I'm really grateful to you, as this item really has got me pondering. I am digesting your information and suggestions - lots to consider there.
One thing I'd be grateful for your thoughts on - in fact anyone's thoughts on - is what could its intended function have been? We've had suggestions including powder jar, covered sugar, bonbonniere and even pot pourri holder. But my two favourite ideas are flower holder or jewel box.
The reason I thought it might be a jewel box is that I saw one of these items some years ago when I was at an antique fair. It's the only one I have ever seen and I only saw it for a few moments. I was approaching a stall when I caught a glimpse of the crown as the stall holder placed it on the table top and then seconds later, as I dashed to get to it, I saw someone else grab it ahead of me. Money quickly exchanged hands and I was left weeping.
Now the thing is - the stall was actually a jewelry stall - full of hatpins, brooches, necklaces and rings. No other glass - just the crown. It occurs to me now that maybe the stall holder had acquired it while purchasing jewelry. The idea of putting your own jewels inside a crown seems possible. Does this have the
ring of possibility, do you think?