very nice Roy - of the seven Registrations on that day - Nos. 318789 - 95 .... this was allocated No. 318792, and is described on the original factory drawing, and in the Register, as 'inkstand'. Unfortunately, another of the purple pencil drawings and despite my best efforts what you will see is the best I can do.
Simon Cottle's book 'Sowerby - Gateshead Glass' names all seven pieces correctly, but as we know from previous discussions on these particular Registrations from the 20th of February 1878, in error the book shows January rather than February as the month of Registration. It does appear than this is Sowerby factory pattern No. 1291, and assume the shape is a diamond of sorts rather than square.
Edited to add....... picture now attached.