Hi Marcy,
As you suggest you can't really go by the cord/cable, as Cogar says it could so easily have been re-wired, possibly more than once, and anyone who wants to use it now would probably re-wire it again. And it looks as if it could easily be anything from Edwardian up to the 20's. Shame about the shade, though. You can find replacements, and hope for a happy marriage, but could be pricey!