Found this via fineleatherworking.com
Old 1930s instructions - thought they might be of use or amuse!
https://bookofjoe.typepad.com/.a/6a00d8341c5dea53ef01348016b9a3970c-pi
Thanks for that @Claire_Lonsdale, feet don’t seem to have changed much since 1937 
I’m inferring that the shoe sizes given are American, so we would probably go up one whole size for an English equivalent.
Shoe size conversion charts are out there, no idea if the sizing in the US in the 30s was the same as it is now!