Nice find, and certainly a rarity, especially with sugar AND creamer, but I'm pretty sure that the sugar matches Davidson pattern 196 (shown as a version with cover in the Davidson catalogues of unregistered designs from between 1880 and 1890).
For some reason, there is no uncovered version of the sugar or a creamer shown in the catalogues, though there is a matching pattern 196 salver and a covered butter shown.
I will try and add some photos from the catalogues for reference tomorrow.
Fred.