It looks very much like what I call - probably incorrectly - a buntline hitch. Glad to see you use it David, 'cos I used the same thing on Aphrodite. I went for a topsail sheet bend on Fantail. Don't ask me why. However, because I'm spectacularly stupid about learning knots from photos or diagrams, I looked up scaffold knot on the Internet to see if I could find something clearer, and they showed something quite different!
If I'm interpreting it correctly, it is a bend using the same principles as the Fisherman's bend (for an anchor), but with only one turn.