The paintballing link looks very promising but is it possible to follow up?
With the present day graffiti on top of the black square it must be very unlikely that the square and letters are original unless the paintballers repainted them but I guess that you and others have thought of that already.
Looking at the photo of the "FH" building it looks (at least on my phone) that the black square could be painted on top of some of the graffiti. When I look at the rest of building, it is strange that the square isn't more covered with graffiti if the square was there first. Also, looking at the condition of the brickwork, doesn't the black square and white of the F & H appear too good to be contemporary with the building's military history.
This may work:-
Go to edit post.
Delete the content of the post.
Add reason for edit.
Click "Edit Topic"
Or in case they haven't seen you post, pm Jack or Joris.
This company only remanufactures customers' dynamos and alternators but it maybe worth contacting them to see if they know where you might find a CAV CB/D8C-47X:-
http://www.vandcautoelectrics.co.uk/product/48/cav-1108510-24v-dynamo
Ron,
What do you think of RAL 085 40 20 and the alternatives?
https://www.e-paint.co.uk/Colour_alternatives.asp?cRange=RAL Design&cRef=RAL 085 40 20&metallic2=False&cDescription=Khaki green
I have read that Mike Starmer's paint colours because they are for scale models are therefore slightly different shades than paint for a full sized vehicle.