Hi LNERGE,
Interesting question, what book is this? ;-) A few years' later, ARM (armour plate) flats were used to support beams, with spacers (conflats or whatever was to hand) in between them. There was a thread just a couple of weeks ago with some pictures, probably from the late 1950s, of a Brush type 2 (class 31) on a concrete beam train, with what looked like WARFLATs. It would be great to see more pictures.
Bill