Today at the virtual meeting of MAGIRT's Map Collection Management Discussion Group, I told about a map of the Antietam Battlefield that was recently "discovered" in the collections of The New York Public Library's Lionel Pincus and Princess Firyal Map Division.  By "discovered," of course, I mean the thing that happens in libraries and archives, when a scholar or other expert in a field finds a resource and realizes its special qualities, whether as an artifact or bearer of information, and explains that special importance and historical context to the wider world.  The thing might have been hiding in plain sight, having been cataloged and valued by its institutional stewards, but it took the subject specialist to bring it to light and distinguish it from other somewhat similar resources.