Enrico, you were sure spot on about this brush being a pain in the butt to restore. Getting the old knot out was easy. After drilling the initial hole, the rest came out in pieces very easily. The hole was initially 25mm with the knot out. That's too small for a 24mm knot, but I didn't want anything smaller, so I decided to open up the hole a bit. That's why I ran into the steel ring inside, as you had mentioned. I couldn't get it out and was afraid of messing up the ferrule, so I needed to grind it. It took quite a bit of grinding with a Dremel to get that ring ground down enough to accept a 24mm knot. I had to go slow because the ring would heat up, causing the ferrule to heat up. I was concerned that the ferrule might be some type of celluloid that might start to burn if it got too hot, or at least some kind of plastic that would deform when hot, so it took a while. The results are good. The epoxy has been curing for a few days, so tomorrow morning will be the inaugural shave. Below is a photo of the handle with the knot out, showing the steel ring, along with the finished product.