good links Milo!
I think that is the boiler group we are lookign at.
Yes there was a gasket, yes it is the expensive one :p
It is usually a paper/ glass based one they get hard and brittle and disintegrate when you remove the heatign element.
Since that has happened you are committed to just fixing her up before the test drive. that is fine.
If you only saw "small flakes" inside the boiler, that is EXTREMELY good news. bad scale means you can grab handfuls, in the literal sense, without any scraping.
I am very much looking forward to the detailed pics of the headgroup and the HX. This is going to be the interesting part!
PS: I do hope to enroll you in the camp that says big commercial HX do not give an inch in espresso quality regarding temperature ctrl. I think the fact that commercial HX are stable (and thus extremely precise) but not with a high degree of control (and thus not so accurate) only means it doesn't matter.
(I have long felt that this .5C temp obsessing they do on home machines and HB is nonsense. temp varies per location and during the shot by many degrees centigrade and that is where a huge commercial HX actually will have far less variance although nobody brags with it...)
Either way you now own in excess of 10lbs thermal mass per grouphead, that beats the real E61 let alone the Spanish knockoff junk.
To Dante (who is surely reading this thread): How do you feel about your temps on the coppertina?