Hello! Did you know taginfo.osm.org? With https://taginfo.osm.org/search?q=naptan you will find all keys used that contain naptan. You can expand the search string: https://taginfo.osm.org/search?q=naptan:m you find
naptan:ModificationDate (696 objects)
naptan:ModificationDateTime (2 objects)
naptan:Modification (2 objects)