Well, the install went well enough, though I cannot for the life of me figure out how to get to that second phillips-head screw from underneath -- the one that is blocked by the plate that holds the steering column to the dash, in later 70's buses. Grr.
I now have a collection of broken switches -- 4 so far -- that have all failed in EXACTLY the same way. I call that a design flaw. So, here is the common failure mode, which I can attest to having taken one apart.
On the "top" of the switch, where the key tang inserts into the switch, there is a small hole that accepts the end of the return spring. The spring has cracked the thin wall adjacent to the hole. In all 4 switches.
However, after taking one apart, I don't think this was a fatal failure. The electrical switch was all crudded up with old oil and junk that is probably the result of people squirting oil/WD40/graphite/whatever into the key slot. But nothing inside was actually broken.
So, I need to put this one back together and do some more testing.
Maybe these all just needed a good cleaning... we'll see... stay tuned...
As for the German switch, time will tell. Wolfsburg West is out of them now, and German Supply, who sells what seems to be the same switch for over $90, says that they are limited to stock on hand. That would not be good if they are not made any more, unless of course these expensive ones fail regularly, too.