Wikipedia:GLAM/National Archives and Records Administration/Catalog links

The US National Archives and Records Administration is in the process of retiring its aging [ Archival Research Catalog] (ARC), the online catalog for the National Archives. Its replacement is called [ Online Public Access] (OPA), and has already been rolled out. While OPA is still undergoing some development, its data is up-to-date and it contains new features, including an improved interface which allows zooming, tagging, permanent links to search results. For this reason, links to ARC should be phased out on Wikipedia and replaced by links to OPA. This will be possible relatively painlessly by replacing the links using a few regular expressions. Below is the key for translating ARC links into OPA links.