A flow chart for authenticating procedures is presented and discussed step-by-step. The first one is stylistic analysis; scientific analysis or technical examination follows, involving materials and manufacturing techniques which are most often considered a source of inferential authentication. Sometimes direct dating is obtained from the materials analyzed, for example by dendrochronology. Direct dating of internal changes accomplished by radiocarbon dating or thermoluminescence analysis can provide limited specific information. More applications of the study of surface alterations to the determination of authenticity may develop in the future. Earlier treatments often cast doubts on the authenticity of some pieces therefore consulting experts is advisable. (Costs are mentioned.)