How can you tell it's real?

In order to protect themselves from forgeries, the early Chinese developed a sophistication in paper making. Marco Polo documented these techniques after his return at the end of the 13th century.

"He (the Khan) allows the inner bark of the mulberry tree to be made into a paste. This is used to make a paper that is very dark and cut into pieces of varying sizes"

Early on the watermark was used as a security measure in the making of paper money. The bank notes of Stockholms Banco in the 17th century, the John Law notes at the beginning of the 18th century and the Sachsen kassenbillets at the end of the 18th century all used this technique. The result of these experiments are still used today.

The Prussians in 1824 used the special paper processessing technique that Sir William Congreve discovered for their bank note. Three layers of paper were pressed together while wet. The middle layer had a colour mark that therefore worked as a watermark.

Another method was developed by the company Giesecke & Devrient: Small, thin paper strips were scattered into the paper in the paper making process . What was printed on these fine strips could only be read with a magnifying glass

The bank notes in circulation in Germany today use a paper with invisible elements for security purposes. These can be read by machines to determine if it is real or counterfeit and it's denomination.