Wehlburg (house) Mark.

The image shows a family- or house- mark of Jürgen Wehlburg, owner of "Die Wehlburg" from 1655-1691. In 1679 he used this mark for instance in a lawsuit as official signature. In times of analphabetism, these symbols were used as such, and had legal validity. They can also be found as mark of property-ownership on door-frames and glass-windows of houses, and on furniture.

(Source: Home-page Jürgen Wehlburg)