Thanks for the kick!
Sorry guys for going MIA - while I was waiting for a new stem to arrive I had to do some unexpected traveling so the continuing repair job went in fits and starts and I and forgot to update the project thread.
Here's where the project stands...
It worked! Patience was the key, but alum was the magic potion. It dissolved the broken, embedded metal without damaging the internal threads needed to re-attach the replacement stem. New stem (Esslinger) cut to length and a perfect fit. The one downside - despite the wax used to protect the white MB star on the crown, it yellowed slightly from the alum off-gassing. I've tried to brighten it up with some concentrated peroxide without success, so I'll move on to a little stronger bleach to see if that may work. If all fails, it's not that big of a deal since the discoloration isn't very significant.
Thanks to [MENTION=93965]junbug5150[/MENTION] 's YouTube video link, I was able to partially disassemble the movement and extract the rest of the stem. Damn, some of those internal screws are microscopic! It all went back together fine, with movement running strong, then...
While fine tuning the stem length for proper crown fit - pulling the stem out and back in each time - the hack mechanism malfunctioned and the darned second hand wouldn't start running again. So, that's where I am now. Fortunately, the same repair video shows the hack repair, so I'm going back in to the movement's innards to give it a shot. This time I'll shoot some pics for posterity's sake and post 'em here. That's my planned project for the weekend - I'll let you know how it goes... I promise! :wink: