Hi,
Welcome to the Forum.
That is a mark used by William Adams Ltd., Compass Works, Birmingham.
Established in 1866 they were still in business until at least the 1930's. They had showrooms in London and New York.
See:
http://www.925-1000.com/silverplate_A.html" onclick="window.open(this.href);return false;
The note I have of their New York address is:
1348, Sixth Avenue,
Hotel Warwick (54th St),
New York.
I wonder what's there now?
Trev.