Many of the items( possibly the majority?) were donated to the museum by individuals. In some cases in the past where land has been donated for a specific purpose and that purpose is defunct then the descendants of the donater has had to be given back the land. Personally I think that a very good thing, and would like it if the same applied to works of art (though have my doubts). , as it would stop councillors defecating on the wishes of donors. Incidently about 45 years ago I donated a very battered torn , pages missing, catalogue of church accoutriments which I had found to the museum, and somewhere have letter of thanks signed by someone or other on the council. They really wanted it at the time as they, at least then, had no such item. No real value commercially, but I would never have done that to an organisation that might then sell things off