[Arran]

Arran

You are scaring the guy

yes the problems are typical but not necessarily encountered. The speaker to be non-working is 50/50, with the field coil being the worst that can happen.
In my first 20 I had to re-cone the speaker and put a new transformer in it, but the field was OK.
In my other 20 Delux.....I think the field coil was bad.
I am yet to look into the plain 20 which Tom gifted me.

Haven't encountered open coils.

To me the nastiest part of restoring the 20 is emptying that capacitor array can. It is truly messy operation. Somehow a similar can in 16 emptied just fine, a can in 111 was a walk in the park, but this one.......nah-stee.

Other than that.......

Mike;
  The open RF coil problem seems to be more common on some models then others, but it doesn't mean that this set has that problem, it does however have the obligatory broken speaker grille. I was trying to remember which issue you had with the speaker in one of your sets, I thought it was either a field coil or an output transformer, you actually encountered both but in different sets. It's not difficult to test either the field coil or the output transformer, and it isn't always an issue. I would think that the output transformer would be a more common point of failure then a field coil, but you never know if or when someone might have tried plugging the set in and BBQing the speaker field so it's worth knowing before you start.
   As for the condenser can, this is where a second hand toaster oven comes in handy, the model 16 and 111 must have had their cans lined with fish paper if they pulled out easily, I cleaned out a can in a Westinghouse and had to resort to driving a large screw into one of the paper caps to pull the guts out as it wasn't lined.
Regards
Arran