this notes have a cool feature:
MicroSam® (Micro Screen Angle Modulation)The self-authenticating MicroSam® (Joh. Enschede) feature is composed of two elements: A microSam screener and a microSam image. The screener is printed in the clear window and the microSam image is printed elsewhere on the opacified substrate (note). They are both composed of a series of fine lines that cannot currently be photocopied; they are finer than the resolution of the eye. The functionality of the microSam® is achieved by superimposing the screener over the image and a hidden message or code appears to the viewer.
The MicroSam® feature provides many security benefits. The ‘hidden image’ is difficult to reproduce using electrophotographic means and provides an anti-scan moire effect. The decoding device, or screener is very difficult to reproduce, obviously it is especially difficult to reproduce on paper-based substrates.
http://www.securency.com.au/en/innovation-in-security-features