Links and useful information!

Recommended reading:

Price guide to mint errors  by Alan Herbert (different editions. 2002) The prices are not relevant but errors are very good described)

The error coin encyclopedia by 1991 Arnold Margolis.

Monnaies Fauteés by Jean-Claude Chort, 2009 (in french,  has very good illustrations)

Mint errors to die for, 2021  Cronin, Joseph 

Useful links: