Filings coherer, glass tube formed into T-shape at one end and bent round into U-shape at other end with bulb, 1899 1899
Filings coherer, glass tube with side pocket mounted on cylindrical rod with brass screw terminals at ends, 1894-1904 1894-1904
Filings coherer, glass tube curved into near U-shape at one end with coil winding at other end, 1894-1904 1894-1904