Can someone tell me about these markings?

British Silver Reading Silver Hallmarks
1

the marks are on the bottom of a mug which has the Sutcliffe coat of arms (Foy en tout), I think. From the site, I think this is pre -1822. Can anyone tell me more about it?

Thanks very much.
silvermug.JPG

2

It’s a Newcastle hallmark. IL over IR are John Langlands & John Robertson. The date is most likely to be 1786 - the date letter for 1810 is also U, but 1786 fits better with Langlands & Robertson’s partnership dates.

3

Great stuff - thanks very much. Here’s the mug itself. Any idea of the worth?
mugfront.jpg
coatofarms.jpg
mugprofile.jpg

4

Value is probably £500 - £800 (assuming a 1 pint size).