Use for quick identification, but verify technical details (watermarks/perforations) against a physical catalogue or a verified digital source like the official postal administration archives.
🔍 Postzegelcatalogi: De Onmisbare Gids voor Elke Postzegelverzamelaar postzegelcatalogi
Major varieties, reprints, forgeries, and significant plate flaws are explained in small print or symbols. Use for quick identification, but verify technical details