coin test
bell·met·al res·o·nance
in cases of a large pulmonary cavity or of pneumothorax, a clear metallic sound obtained by striking a coin, held against the chest, by another coin, or by flicking the chest wall with one's fingernail; the sound is heard on auscultating the chest wall on the same side anteroposteriorly.
coin test
A test for pneumothorax. A metal coin is placed flat on the chest and struck with another coin. The chest is auscultated at the same time. If a pneumothorax is present, a sharp, metallic ringing sound is heard.