I've just added "Old Silver Platers and Their Marks: Being a Copy of the Register of the Sheffield Assay Office of the Persons Concerned in the Manufacture of Goods Plated with Silver" to the website. It was published by the Sheffield Assay Office in 1908 and includes 134 mark illustrations dating from 1784 - 1836. The introductory text by Bernard William Watson is well worth reading. In the original the marks were charted chronologically, I've reordered them alphabetically for easier reference.
Hope you find it useful.