Without research I would speculate that as a control, it was used to 'dial up' a transmitter and control its functions. There is much missing, a chassis of relays and the like? There is a series of transmitters named 'FRT'. It could also just be part of a simple phone patch or audio panel.
http://www.virhistory.com/navy/xmtrs.htmBack when the bell system was the internet, a rotary dial was sometimes used to enter a series of numbers that would select a function such as a switch or a voltmeter, etc., then interact with it by providing a reading or by operating the remotely located device. At each end of the (leased) line, there was a modem with a meter or control outputs.
This opinion about it being more sophisticated is based on what my elmer, as a chief electronics engineer with Braniff International Airways, had told me about how he regularly would dial up a transmitter to take readings or control it or interconnect/patch it in a HF net. I believe this was a product of Collins, as he always talked about Collins.
