When this thread started I went out to check the seatpost sizes on my bikes and noticed something. My '38 Bates has 531 Plain Guage with a 26.2 seatpost as does my '70 Jack Taylor. When I took out the posts to check their sizes I noticed that the wall thickness of the Bates is about 2mm whereas the wall thickness on the Taylor is almost paper thin. Difference in manufacturing Plain Guage or is it something Norman did to the tubes? And why?