„The arms were granted in 1926.
The village became a boom-town at the end of the 19th century, due to the coal mining. It became a city in 1919. The village only used a seal with the Prussian eagle. The arms show a symbol of the coal mining placed upon the cross of the Teutonic Order. The loge of Welheim of the Order owned the area from 1230 to the 18th century."
This image is based on a depiction from NGW.nl.
Original: Unknown Vector:  Jürgen Krause