Silver assay date marks provide the most accurate method for dating silver pieces, using systematic letter codes that change annually at each assay office.
Each assay office uses a different alphabetical sequence, typically running A-Z over 20-25 years before starting again with different fonts or shield shapes.
The style of the letter, the font used, and the shape of the surrounding shield all contribute to precise dating. Reference books and databases help decode these systems.
Date marking systems evolved over time, with some periods using different cycles or additional symbols, requiring specialized knowledge to interpret correctly.