Extract from the letters patent granted by Emperor Friedrich III, dated 9th December 1467:
"[...] The following crest and jewel, namely a vertically divided shield, the left-hand half being white and incorporating a red clambering wolf with slavering tongue, its tail in the air, and the other half being red, incorporating from the base a white castle wall with five crenellations and beneath them two arrow slits with a black gate that incorporates a golden portcullis; emerging from the middle of the wall there is a white un-roofed round tower with a window and above it three crenellations; on the shield is a helmet decorated with a white and red helm roof.
On it is also part of a white castellated tower as also illustrated on the shield and emerging from this half of a red wolf, its tongue slavering and poised to throw a white stone which it is holding in its right front paw [...]"
The full transcript of the letters patent relating to the coat of arms may be found and downloaded here in PDF format.