It is a regular 'Rietz', but rather small with a 12.5 cm scale. This one looks and feels absolutely new and unused, the leather sleeve is pristine as well. The only marking on the back indicates it was intended for Heemaf, either for use by the company or perhaps more likely meant as a promotional gift. The overall look and feel makes me guess this could be as recent as the seventies, but hard to tell really.
In the small leather sleeve with the small sliderule comes one sheet of instructions folded up equally small. A very condensed course in using this system 'Rietz' sliderule (in Dutch).