There is now evidence from two late cars – 1937 – that suggest that Austin screens were to this pattern, in two folding pieces. Very different to the other, more common, pattern parts from aftermarket suppliers, as they were designed only for use with the wind deflectors also fitted to 1937 cars. Many cars have been retrofitted with side screens as per the other post here – fitting in the entire space between hood, door and windscreen.
Can you add more information to support the hypothesis? It is suggested that all other patterns are aftermarket, and that cars prior to the final year of production were not fitted with any screens, other that ones which local dealers might have organised.
Thanks to Jim Blacklock for these images from 1986 – a real find.