Aha, well that explains some things! If the machine was purchased in the UK, i.e. designed for the UK market, then the U.S. voltage motor that's on it now was certainly added once the machine was back here in the 'States. And I'm betting the 1930s-era Singerlight was also added Stateside as well, probably in, as Muv pointed out, a shop with those parts in stock. It still doesn't explain the outdated tension and faceplate, but perhaps those were replaced due to damage? I guess we'll never know, but it's fun to guess.
And Thayer, thanks for taking the time to put up those photos of the different bobbin areas, I found it illuminating and I know it's not a trivial thing to just slap those images together.