I have one of the these too. They were standard IBM IO Selectrics, modified electrically for what appears to be use on a military aircraft. I'm planning on building a serial or USB interface for it so I can use it as a remote terminal for my IBM 1130 simulator. I've gathered a lot of information about it including the connector, signals etc. If you're interested, let me know and I'll send you what I have. These machines being sold on eBay, by the way, are in wonderful shape mechanically but most likely have a shorted or open control soleloid. Brian