Hello.
As GPS referenced, here are three of the threads on the certificate/reproduction:
https://pinside.com/pinball/forum/topic/green-gottlieb-certificate
https://pinside.com/pinball/forum/topic/-manufaturer-cert-for-kings-and-queens-
https://pinside.com/pinball/forum/topic/question-about-1960s-gottlieb-manufacturers-certificate