Printing on bottom states, "727-42, US Navy Yard, Charleston, SC, May 14, 1942, Rear view of fluxmeter panel board Drum Island, Magnetic Channel Range. File 12821."
Under tab, "Degaussing 1942" Printing on bottom states, "728-42 US Navy Yard, SC. May 14, 1942. Rear view of fluxmeter panel board showing detail of calibration and control wiring Drum Island, Magnetic Channel Range. File 12822."
Under tab, "Degaussing 1942" Printing on bottom states, "725-42 US Navy Yard, SC. May 14, 1942. Front view of fluxmeter panel board Drum Island, Magnetic Channel Range. File 12819."