I picked this up today in Llano, Tx. There is a railroad museum in Llano and they had one of these on display in there. I was able to contact the person who donated it and they had another one. It has the paper schematic drawing under the lid and it is stamped with CB&Q RR. ........which was the Chicago Burlington & Quincy Railroad. They apparently used these to splice into the telegraph lines and call from just about anywhere along the railroad. Does anyone know anything else about these things or have you seen many of these?