Error-ref.com is a comprehensive illustrated glossary of every conceivable defect associated with the minting process. It will contain detailed illustrated descriptions of hundreds of basic error types, numerous subtypes, and assorted effects associated with them. It is not designed to cover compound errors and multiple errors, as these occur in an infinite number of combinations and permutations. It is also not intended to be a catalog of specific coins and dies.

The Ready Reference is built upon a framework provided by a 22-page Comprehensive Error-Variety Checklist that was compiled by Mike Diamond some years back and that he continually updates. The checklist is available on this website.