It looks like a different saddle with longer springs (beehive underneath?). The B73 is like a B66 but with a spring in the front instead of a fixed rivet. The Superior ad talks about a Brooks tourist saddle and shows a 73, but I cannot recall ever seeing one on a post-war Superior. That gold Superior is an unusual color!
Yes - that's a B73 frame. So it seems at least some of the bikes came with the the triple spring. I have one of those saddles in a box somewhere around my place. I should see how it goes with the green Superior I have. I've got a light brown B66 on there for the time being. Thank you for finding that picture.
Edit: and the one you found has the tapered clamp as well.