e g permanent yellow h10g hansa red 3b hostaperm green 8g or hostaperm blue ar all registered trade marks on the firm of hoechst varnish colored pigment and the coloring agent according to the invention were intimately mixed on the three roll mill the printing ink obtained demonstrated its suitability for bank note guilloche printing they can be used in all printing techniques which are used for printing securities particularly for steel gravure printing a preferred testing method for security papers with authenticity characteristics according to the invention is checking undertaken simultaneously and at the same place of the magnetisability and ir transparency which if desired can further be supplemented by a corresponding measurement of the absorption in the visible spectral region suitable testing devices for carrying out this process are basically known thus already u s pat no 3 612 835 describes a measuring head with which simultaneously and at the same position the magnetic properties and also the absorption in the visible spectral region can be measured for this the gap in the magnetic head is filled with a transparent material which extends up to a si photodiode built into the interior of the magnetic head with small modifications this test head can also be used as a testing device for security papers according to the invention for this the material which is transparent in the visible region and arranged in the magnetic gap is replaced by an ir transparent vis absorbing material e g a glass such as schott rg 1000 trade mark or silicon or germanium these materials are non transparent.