Sources & Methodology
All date letter mappings in this database are transcribed from public-domain sources and official assay office statements.
Primary Sources
CH
Chaffers' Handbook to Hall Marks on Gold & Silver Plate, 1924 ed. (revised by C. A. Markham)
JK
Jackson, English Goldsmiths and Their Marks, 2nd ed. 1921 (Dover 1964 unaltered reprint scan)
OFF
UK assay offices' own published statements (see SOURCES.md)
Methodology
Cross-Reference Approach
Where possible, we cross-reference multiple sources to verify accuracy. Each entry includes:
- High confidence: Both public-domain sources agree on the letter and year
- Medium confidence: Only one source available, or letter form/case differs between sources
- Low confidence: Sources disagree on the year
Excluded Data
Some date letter series have been excluded due to source disagreements:
- York: Only one public-domain table (Jackson) with long gaps; could not cross-check
- Newcastle 1702-1790: Chaffers and Jackson disagree on almost every year
- Chester pre-1701 and 1751-1775: Sources disagree on letters, case and years
- Dublin pre-1821: Sources disagree by one to two years throughout
- All offices 1925-1974: Not covered by any pre-1929 public-domain book
Alternative Readings
When sources provide different readings for the same year, we show the primary reading with an "alt:" notation for the alternative. Users should consider both possibilities when identifying unclear hallmarks.
Data Format
The complete dataset is available as JSON at /hallmark-date-letters/data.json for developers and researchers who want to build on this work.