What is “Chelsea-Derby,” and what happened in 1770?

Chelsea-Derby refers to porcelain associated with the period after William Duesbury, owner of the Derby factory, who has purchased the Chelsea factory in 1770. The British Museum describes this Chelsea-Derby period as lasting until 1784, when the Chelsea factory site was demolished. Britannica gives a similar story, noting a sale to James Cox in 1769 and then to Duesbury in 1770, with production continuing until 1784. This period brings objects that may look similar to products from both factories, making them more difficult to attribute. Marks may combine ideas from both factories, and shapes may vary between factories.