I can see the 1938 parts lists in Library search but does anyone do a parts book with exploded views, so you can hopefully see which part joins to which in these prewar bikes?
The pre war BSA parts lists were not specific to any model. Each year covers the whole range of models, but are illustrated and essential. There are plenty out there if you google it.
https://www.ebay.co.uk/itm/261670602399?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=CjwKCAiA_5WvBhBAEiwAZtCU7xUug3K0Cly6M3nrnNetC-xIINbjFXZ3m5cjJw_UsP088h9fX5CSCRoCqNEQAvD_BwE
https://www.classicbikeshop.co.uk/bsa-1938-parts-book-all-models.html
Ron
The exploded view parts books were not issued until 1953.
That's a shame. I contacted Drags to see whether they did one, but they just have the standard parts lists. They do however have individual exploded diagrams on the website for girder forks for example from the late 30s.