Can anyone ID this cypher?

I have strange item this originated from a Whitley crash site some time ago – it looks like a book made up of aluminium alloy and hinges open. Inside the rows and rows of stainless steel wires. Tiny letters on blocks – much like those of a typewriter – run up and down the wires.

We think it was used for deciphering codes, but this is outside the usual realms of Whitley airframe parts and I have never seen one before.

Can anyone supply more information please?

Cannot supply a pic yet as i haven’t been able to take a decent one.

Thanks in advance.