This is a silver plated plated plate clip made by Walker & Hall in 1910. It is larger than the usual fish bone clip. It is actually pictured on a side plate, so it it not as large as it might seem, but it is still the biggest one I have seen. Would anyone have any ideas for it purpose. Dipping sauce is top of the list at the moment, but I am not sure about Edwardian Dim Sung.
It would appear from searching online that Walker & Hall may have taken out a Patent on this device, or something similar. Viewing an old auction catalogue from early last year revealed a set of four clips assayed at Sheffield in 1903 by Walker & Hall, that were also marked 51208 and PATENT 33. These clips measured 9.5 cm, I'm not sure how this compares with your example.
It would be interesting to see exactly how W & H described them in their Patent application.