Abstract: An object of the invention is to provide a pocket sized instrument for reliable recognition of authenticity features of banknotes and other security documents. A basic embodiment of the instrument includes an elongated rod with a handle part at one end. The handle part contains the battery housing and the switch and is provided with a clip for facilitating handling. The other end of the rod includes a frontal test part. A banknote can be passed through a slit in the frontal test part and exposed to the enclosed optical elements. Authenticity features of the document become visible through illumination.