can't tell by looking, at least us mere mortals can't. I'm inclined to trust that Raleigh would have spec'd BSC threads, but do you *know* that it's the original wheel? In this case, I'd try a known British lockring or FW and grease it up good before trial. Don't go past the point of hand torque-ing; if it doesn't jam up within a few turns, it's probably a "go". Thing is that the difference between FR and BSC (34.7 x 1mm and 1.37" x 24tpi) is so close you really can't tell by measuring with common tools, and the real crucial difference is in the thread *angle* which you would only see in a magnified cross-section. But you can tell right away if you test it by simple go/no-go trial.