Volume control with five positions Made from dark brown Bakelite. The volume can be adjusted in 5 steps with the ribbed knob. The Philips Radio logo and the text "Ned.O.a 57409" are printed on the front and back of the plug. This patent number is from 1931, it was extended in 1934 and it expired in 1954. The inventor was Willem Six. The official name of the patent was: "Device in particular for the control of loudness in low-frequency distribution systems".

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