I've done a lot of research to positively identify this piece; a large sterling silver tankard made in London.
The date mark is a lowercase 'd' in a simple shield, which would suggest either 1779 or 1819; those marks are so similar, its hard to tell. The style of the "WC" initial mark (and the design and craftsmanship of the piece) suggest William Cripps (1731-1767) but the dates don't line up. I guess it could be William Cattell, with a likely date of 1779 but I would very much respect and appreciate the opinions of forum members who might know better.
Thank you!
![Image](https://www.925-1000.com/pics/Ximg.jpg)
![Image](https://www.925-1000.com/pics/Ximg.jpg)