Having many samples on one medium, it is difficult to keep the overview and to didicate the results. In order to simplify this, we have developed a new production series of cloning cylinders, which are continuously numbered. The four-digit number code makes it possible to cleary dedicate up to 9999 samples. By the laser-imprint process the markings are worked irreversibly into the glass, which leads to the benefit, that the markings can not be removed despite strong solvents and pyrolytic disinfection.