Peter- single brood only. And this was verified by the Guinness Book of World records. Aebi (I spelt it wrong above) and his son were great beekeepers, loved bees and wanted the record for fun is my guess. Certainly would have helped sell books too. Though they hold the record others have exceeded it- notable in Western Australia in the 1950’s. Before we knocked a lot of the forests- fools that we are.
Reading how they managed 5 supers on a single brood is interesting and the methods is similar to what this forums own @Doug1 from canada achieves in his short season with 5 flow supers on a single brood box… !! Though he uses two queen hives. Complex stuff.