I want to revisit the Doukas icon for a moment or two. I was wrong it isn't riveted to the Crown now, it is soldered with soft soldering (it should have been done by hard, or maybe brazing - not sure about the correct term, but I think gold hard soldering differs somewhat to brazing -, I read this type of soft soldering eats away that gold in humid conditions, so now the crown was put in a controlled environment to pause the process). But it was riveted there earlier.
This enamel plate also has other curiosities, that three holes above Emperor Michael's head. The one on our right a weird shaped one, like a pear, lightly touches the halo and it has a proper rim. Above that little to the left, that's punctured hole with jagged edges. To our left the third is right on the halo, but this one is really strange the outside edge has a rim but the inside doesn't, in fact it cracked the enamel.
We have older pictures of the crown, photos and drawings. Here's two which are more than 100 years old. You can see, that the hole on the left, it doesn't go into the halo, it's a half circle and has a rim where it touches the halo. So that whole was drilled through. And on the other side it went through Saint Thomas' icon behind the Doukas disk. You can see on pic #3 that the gold strap was punctured twice (the lower two holes) even the burr around them are observable. But the burr means they weren't even used!
And lastly, just to show how big is the Doukas icon... they had to remove the line of pearls below to fit it there. Apparently it's 26% bigger than the socket behind. It's obviously wasn't made for that, this size can't be a mistake. A millimeter or two maybe, but not this.