What's it off part 2 – seat

Here’s another query after the success of identifying the Lincoln escape hatch.

This seat back has the armour on the inside. There are no numbers or stamps that I can see other than a solitary ‘4’, without removing the armour and checking underneath. The plate on the rhs refers to TR9F Special – Normal switch. Any ideas ? It came from a now defunct recovery group and was with a stack of Wellington parts, but having said that there Hurricane parts in amongst it too.

Jeff