I am confused by you edit to Help:Copyrights: "25 years after publication (Q29940790) - applies to formerly unpublished material in the Netherlands, probably other countries as well". "Formerly unpublished" material becomes PD 25 years after publication? Is there Commons template for this case?
Topic on User talk:Hannolans
It's a strange article in the Dutch copyright law. Never seen a case about this, but expert Dirk Visser mentioned it here https://www.ie-forum.nl/artikelen/verdwaasde-werken
This is the article:
https://wetten.overheid.nl/BWBR0001886/2014-10-29#HoofdstukVII
Hij die een niet eerder uitgegeven werk voor de eerste maal rechtmatig openbaar maakt na het verstrijken van de duur van het auteursrecht, geniet het in artikel 1 genoemde uitsluitende recht.
- 2 Het in het eerste lid genoemde recht vervalt door verloop van 25 jaren, te rekenen van de 1e januari van het jaar, volgende op dat, waarin de eerste openbaarmaking van dat werk rechtmatig heeft plaatsgehad.
Ah, 25 year is part of the European Directive.
Article 4
Protection of previously unpublished works
Any person who, after the expiry of copyright protection, for the first time lawfully publishes or lawfully communicates to the public a previously unpublished work, shall benefit from a protection equivalent to the economic rights of the author. The term of protection of such rights shall be 25 years from the time when the work was first lawfully published or lawfully communicated to the public.
https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:32006L0116
Mentioned here https://en.wikipedia.org/wiki/Copyright_Duration_Directive#Previously_unpublished_works
Not sure if this is 'copyright' or neighbouring rights and how Wikimedia deals with this right on Commons
It sound like copyrights and it seems that anything which is unpublished and in PD could become copyrighted if someone "officially" publishes it. Crazy.