Gretchen caught Ruby pointing, at which point (no pun intended) we started considering various breeds of pointer as part of the mix. And while that's a possibility, it doesn't really explain the very shiny coat or the rather fluffy undercoat that Gretchen has noticed.
And about a week ago, I took a good look at Ruby's tail. This is not the tail of a pointer or a Labrador retriever. This tail is sort of halfway to being feathered, with a curve of hair sticking down from about halfway down the tail and curving back to the tip. I recognize that tail conformation. That's a setter tail.
Well, a setter will point in much the same way that a pointer will, so that's consistent.
I'm strongly suspecting that Ruby is half Lab and half Irish setter. And here, for example, is a dog looking very much like Ruby, save for the fact that the Lab was obviously a chocolate Lab instead of a black Lab.