Banknotes are attractive targets for counterfeiters because of their high face value. Over time, since they first appeared in China in the tenth century and in Europe in the seventeenth century, banknotes have acquired more and more sophisticated security features to deter counterfeiting. Security features began with complex designs and individual signatures and seals, and then moved on to watermarks, fine engraving, printed serial numbers and coloured overprints. In the 20th century a number of security features, ranging from embedded metal threads to intaglio printing, came into use.                     Chinese paper money from the Song Dynasty (960-1279) Early European note (with 8 seperate signatures and several seals) (1666)   $1 note of The Hongkong and Shanghai Banking Corporation (1872)