Provided is a coordinate measuring device for sensing a location of a coordinate indicating device including a resonance circuit. A bearing surface is formed between two chip grooves which extend along the associated main lip of the respective side surface, said bearing surface extending symmetrically beyond the groove ends of the adjacent chip groove and transversely to the main lips until its adjoins the latter. Also disclosed is a leak testing apparatus for detecting a leak gas in a flushing device. 6, and the y1 satisfies 0\u2266y1\u22660.