Just picked up a Fisher 400 receiver. Very high s/n 81130. Don't remember seeing a s/n that high. Every tube is marked Fisher except for a 6AB4 (Westinghouse). Most of the tubes are German except the output tubes. Found in an old barn. I've done no cleaning on it yet. It's very dirty. Only part of the cabinet remaining is the bottom. Of course missing the metal knob caps and one of the slide switches is broken (loudness/contour). Does anyone know a replacement source for the slide switch? Attached are some photographs. Thank you.