"Property description" is a predefined property that allows to describe a property in context of a language and is provided by Semantic MediaWiki. This property is pre-deployed (also known as special property) and comes with additional administrative privileges but can be used just like any other user-defined property.
ID of the online catalog of the American Numismatic Society Library (en) +, ID des Online-Katalogs der Amerikanschen Gesellschaft für Numismatik (de) +