For the 1996 series a watermark was added to the paper. This is also not a new invention. Watermarks were first used in the late thirteenth century in the handmade papers of Italy.

The first watermark that originated on paper was in the form of an F. and was produced by a mill in Cremona, in northern Italy; it dates to as early as 1271 and proved useful for identification and ...

This sheet of handmade paper comes from the Fabriano Paper Mill in Milan. In regular light, it looks like a blank sheet but when you hold it to the light, the watermark becomes visible. The image, ...