A dating system consisting of gas sample counter with internal anticoincidence counter ring, transistorized electronic equipment, and chemical apparatus was developed in the Institute (Felber and Vychytil, 1962; Felber, 1965). A high voltage supply Fluke Model 408B is used. For routine dating, begun in 1965, an improved 2.4 L counter with Teflon insulators is used, shielded on all sides by 20 cm of iron. The counter is run with methane at 760 torr/15°C. Spurious counts are carefully eliminated by a systematic procedure (Felber, 1966). Stability of electronics and counter is checked once a day by taking the topmost part of the peak of Mnα-X-rays following electron capture in Fe-55, radiated through a beryllium window. Checking is done with the same single channel analyzer (switched over to operation with small window) used for energy discrimination (switched over to two discriminator operation) during measurement. If any change should be observed, discriminator settings are corrected. Energy discrimination is not optimized (Felber, 1962) because a neutron generator using (d,t) reaction is run in the same building in which the samples are prepared: the lower discriminator is set above tritium maximum energy at 22 keV, the upper one at 120 keV, the highest possible energy absorption of C14 β particles in the special counter. The background is 1.58 cpm, the net contemporary value (95% of NBS oxalic acid standard activity) is ca. 8.8 cpm.