Walt's 1934 drawing is very interesting. The right barrel shows a typical WS1 configuration with the exception of the .006 leading overbore. The left barrel shows a typical .011 improved cylinder or WS2. The .735 bore size right before the minimal choke in the right barrel is apparently a short overbore of .006 right before the choke. I'm not sure whether the WS1 has this leading overbore.