Prototypes
Type 4 prototype information is very hard to come by. Here is the few snippets I found so far. This page shows the 411 Cabriolet prototype manufactured by Karmann in Osnabrück and the 411 notchback prototype, also known as EA 142.
The VW 411 Cabriolet prototype
411 Cabriolet: retractable roof
411 Cabriolet: rear view
411 Cabriolet: dashboard
411 Cabriolet: passenger side
411 Cabriolet: View through the passenger door
The VW 411 notchback prototype (EA 142)
EA 142/411 notchback: passenger side
EA 142/411 notchback: Another passenger-side image
EA 142/411 notchback: rear view
EA 142/411 notchback: frontside detail
EA 142/411 notchback: engine compartment
EA 142/411 notchback: dashboard