Hi Richard,
That's a really neat little engine! I like the copper boilers, too -- kind of a nice departure from the nickel plated ones. I'm guessing this also helped reduce the cost a bit for the manufacturer. It will oxidize over time, but since you can polish it back up, it's a good deal. Once nickel goes bad, there's not a lot you can do to restore the original look other than re-plating.
I also like your variac transformer. It's great to have, especially for engines that don't have a throttle.
Nice work!
Paula