WW2 RAF (Air Ministry) Spitfire Aircraft Radio Power Unit Type 87, No 10K/201, Rotary Dynamotor Motor, Which Powers the Aircraft Radio Transceiver. 

Rare and original. 

Dated around 1940

Power Unit Type 87, Ref No 10K / 201 A.M. (Air Ministry) 24 Volts, Serial 22388

Internally marked: A.M. Rotary Transformer, Type 52, Ref 10k / 568

Input 24v 

Output 6.5v / 2.5A - 250v / 50ma

Potentially still in working order, untested.

You may find the following related video of interest

https://youtu.be/HUWp_tivnzI?t=42

Good used condition for age, with some wear, marks, discolouration and scratches. 

21cm x 17cm x 11cm