Hi thanks for writing in. These are UK hallmarks. Great Grandmother's, uhm.. was your Great Grandmother Scottish? The other symbol is important, it will tell you where the mark was registered - the sponsor could be William Crouch & Sons - Silversmiths, Edinburgh, Scotland, Uk ca. 1870s.
The "b" letter is the date letter, this letter will help you confirm dates and registry office. Check this letter with the date letters - you will see a link to the date letter charts on the researching British Hallmarks page. Check the Edinburgh, Scotland date letters "B" and the Birmingham date letters "B". Here is a link to the Researching British Hallmarks page
Everything must match including the shield the letter "B" is in.
