Hello,
You can find a copy of the badge you are looking for if you go to the following URL.
http://history.farmersboys.com/Posti...lin%20DERR.htm
I am afraid my IT skills were not up to copying it across.
There is a museum in Berlin on the Allied Forces there after 1945 that you might like.
http://www.alliiertenmuseum.de/en/0.php
Are you considering painting your Ferret in the Berlin Urban Scheme with all its blacks greys etc. in squares?
Regards
Nick Balmer