A pinch grip hanger mechanism dispenses pinch grip hangers, one at a time, and then opens the pinch grips for insertion of a garment. A combination of swept frequency acoustic interferometry, wide-bandwidth, air-coupled acoustic transducers, narrowband frequency data acquisition, and data conversion from the frequency domain to the time domain, if required, permits meaningful information to be extracted from such fluids. Protruding from the interior face is an insert shaped to fit into an opening of a firearm slide.