Cancelled but no Postage Stamp

This is a postcard sent to my Grandfather during the WWI here in Namibia, which was then known as DSWA - Deutsch Südwestafrika.

The card was cleared by censors. What intrigues me is why there was no stamp on it?

I thought perhaps the stamp had been removed, on inspection it was clearly never stamped.
Just a little tidbit of interest. - i will post something more recent next time.