I wonder at what stage in the build the Raleigh frame numbers were allocated & stamped? For some reason I'd expect the number to be stamped on completion of the fabrication, yet the frame pictured by
@midlife must have been stamped before the rear stays were added, otherwise you wouldn't be able to get the tools in there! It's also odd why some were stamped on the BB and others on the seat tube itself or seat lug. Were "quality" frames (such as 531) treated differently in this respect than the run of the mill 18-23 HI-tensile ones?