The Nomisma collaborative project provides stable digital representations of numismatic concepts and entities according to the principles of Linked Open Data. The representations take the form of http URIs that provide access to reusable information about those concepts as well as links to other resources. Nomisma offers several REST APIs for developers. They include Average Axis, Average Diameter, Average Weight, Closing Date, Get Label, Get RDF and Get NUDS. Response data is formatted in XML.