Looks Smart!
I've got a number of 370 Juniors and I also haven't seen one in the flesh, which has been polished up like this.
My theory is that they weren't polished up like this in the factory and that someone has done this more recently in the machine's history. Of course it's possible, as you say, that Hoover might have done this as a Special..but then the machine would have needed to be kept repolished somewhat to maintain this sort of gleam surely?
Is there any reason why you can't take a rather faded 370 and buff it up in this way? Perhaps I'll give it a go when I get chance?
just my thoughts,
Stephen