You are a London auction house. You have been approached to appraise and consider selling a ‘Benin bronze plaque’ [actually brass!]. You have been told that it is now in a private collection in Antwerp, but that the date it entered the collection is unknown. You believe that the mask might be the same one as having been recorded as sold in London in the 1920s. What due diligence would you carry out? What legal and ethical issues might you encounter and how would you address them.