hard to tell without a photo of the mark, and seeing the image of the shield if it's in a shield; Glasgow scotland, Sheffield, etc. there several registered WM maker's marks, some with ampersands, some with decimal points between the letters, etc.
WILMOT MFG Co. were manufacturing silversmiths, in Birmingham, W M initials however the date doesn't match with date you mention. WM - Wilmot Manufacturing company ca 1912 - 1950s.
