I found mention of this on another site and was made to understand it is useful. However, my German is limited so perhaps someone here can provide a few more details about how to properly use it.
http://www.stampsx.com/ratgeber/stem...on/zeichen.php
To the right of the word "Land" click on the down arrow and scroll down to: 248 Deutsches Reich 1933-1945.
Usual disclaimer,
Ed