The Projection print scale is a wonderful thing. I think Kodak invented it, but like Kodachrome, they must have let the patent lapse. .
It is hard to describe in words, but essentially it is a bunch of neutral density filters (segments) that show the result if you use an exposure time that corresponds to that segment. In other words, if you expose an image through it (for the 60 second time recommended), the segment that results in the best range of densities on your test print, will correlate with an exposure time that will give you an excellent starting point for your exposure tests.
I think they are a much more useful aid for BetterSense, then they could ever be for someone like Vaughn, simply because they are great for getting you into the "ballpark", and, well, Vaughn is probably already in the "ballpark" anyways .
If you cannot find one, BetterSense, send me a pm - I may have a couple extra of these, which you could have for postage.