P2 Rear Seat construction

[RobHomewood]

I am trying to refurbish the squab of my rear seat as it is looking a bit saggy. When I opened up the leather I was surprised to find a honeycomb type foam rubber cushion in there. Does anyone know if this could be original? It seems in fairly good condition but it could have been fitted by the previous owner. This is a 1939 Salmons Tickford P2 and these coach build versions do differ in some details to the standard but I would be surprised if foam rubber was used in car seats 80 odd years ago. Any clues?