Today I JUST worked on my husband's signet ring. The Plan is to get the ring itself done by the end of the week (like, Friday), then do the enamel over the course of several days, then set and finish it. This seems possible. There is a deadline of Thurs or Fri next week, if he is to wear it to the conference, so I need to get my butt in gear! Still, the trickiest parts of the assembly are now done, and the enamel ought to go relatively quickly (she says optimistically).
Today I spent 2 hours fighting with the bearing, and I have a renewed appreciation for the method Fretz describes! Still, I didn't have the mandrel, so that wasn't an option on this one- and I'm pretty proud that I got the sheet bearing fitted and soldered in.
Since the interior of the space is very complex and rounded, the sheet didn't want to stay put even after it fit. I was hoping to get it wedged in, then solder, but nope- wasn't going to happen. So I figured out how far down it was, cut a strip of thin copper that width, coiled it up, tweaked it some, covered it with White-out (the water-based makes a good solder resist, though you need good ventilation), then put it on my soldering block, put the fluxed ring over it, inserted the fluxed setting from the back, added lots of hard solder just to ensure I wouldn't have to do it again... and it worked like a charm.
The next steps are the enamel, and fitting the inner sleeve into the outer skin. I shall start work on them tomorrow.
I am feeling pretty accomplished, especially since the whole approach was rather a kludge to compensate for not having the right mandrel.