All told, there were actually three such signs, although one was made of wood - it stood in the centre of public square Reichsschatzmeister-Schwarz-Platz (known today as John-F-Kennedy-Platz).
The post featured in the image above was integrated into the outer wall of the larger camp zone - not the boundary of the Häftlingslager (prisoner camp) and almost 1km from the actual KZ. It directed east - toward the main camp entrance. The other directed towards the western entrance and the SS drill area.
The image was taken by SS photographer Friedrich Franz Bauer.