Abstract: The present invention is directed towards a security sheet and a security booklet comprising a security sheet. The present invention is further directed towards manufacturing a security sheet and security booklet and a method of authenticating a security booklet. The security sheet comprises a plastic substrate having first and second outer surfaces, at least one opaque region at least partially surrounding at least one window and perforations extending between the first and second outer surfaces. The perforations form a first data element located partially in the at least one window and partially in the at least one opaque region.