London Mark, Sterling Mark, Date Mark n1788, makers mark I.S

[gil957]

Greetings! I can't find this maker. The period between the I and the S is midpoint and not at the bottom of the letters. Sure some of you will know off the top.
Thank you in advance. Sincerely Gil
HAPPY NEW YEAR[/b]

[larkfield]

Without seeing the punch mark or knowing what the item is, John Scofield would be my first thought. James Stamp is a possibility, but 1788 may be too late, the latest piece I heard of was 1785

[nigel le sueur]

l cannot see an image on your post, where was this item assayed and any dates l S is quite a common mark.
Also when you say "period" is that what on this side of the pond we call a "pellet" :-)
Nigel