Xk120 Door panels and under dash panel

What was the underdash and door cards made out of on a xk120 (original).
Also did they alternate the between materials later on?

Underdash the original I have from 1952 roadster bituminous card but believe later fhc dhc were ply
Doors bitumised card
Bootlid I have both py and bitumised card

Yes I thought this thankyou! Just double checking ply seems to be more stronger than millboard:)

My '51 FHC has 1/8" plywood.

Yes think ply is stronger thankyou!