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
Filings coherer, glass tube bent into U-shape at one end with bulb to form side-pocket on mounting bracket with terminals, 1894-1904 1894-1904