[RolandF]

I don´t think this one should be used outside. The small holes on the side surfaces might indicate the whole brick ought to be embedded in mortar.
Looking at the dimensions I think this was intended to be used for wall coverings of hangars and workshops. Please could you give the exact size in millimeters to compare it to the "Reichsformat" normation?
In contrary to usual glazed tiles those "bricks" are used like real bricks; that means the wall is built up by using those glazed bricks with one or two unglazed ones in between. The hole on the backside is for better handling and less weight.

Regards

Roland