This is what the boiler looks like on the inside, browned and stained but still pretty clean. When I rubbed my finger against the stain above the water line it had no smell.
Here's a close-up to show the nuts holding the taps in place. It's a shame these fasten from the inside so one has to remove the back of the boiler to service them.
Another design feature that prevents tightening the taps from the outside is the length of the dipper tube, which extends beyond the circumference of the boiler. That's a shame. Otherwise one could turn it from the outside, checking to see that it's pointed downward by reaching in through the group port with the group removed.
This close-up of the water tap shows the service I want to secure to a smooth, unthreaded port. I think I'll use food-safe Loctite thread sealer where the nut threads onto the tap and inside the smooth hole and where the gaskets push in, hoping this creates enough friction. If not I'll have to apply a larger amount of JB Weld to the outside, because the first application didn't hold.
I also noticed the beginning of scale, even though I've been using mostly distilled water. This means I'll need to keep up with a descaling regimen.
Scale tends to build up especially where there's heat, as you can see here at the heating element terminals inside the boiler.
And here's a photo of significant rust that had already started developing in the bottom boiler bolts. These had been exposed to some early leaks during initial testing. This amount of rust formed despite their being coated in anti-seize compound. I'm now ordering marine grade stainless replacements for all of this hardware. I've revised the section much earlier about hardware selection to show the need for stainless.