It started life as a dial unit for a Magicall dialer sold through the Bell System.
It looks like it fell prey to a hobbyist that hacked it for some purpose we can only guess at without tracing the added/modified wiring.
If you want to research the original unit in the TCI Library, try a Google site search for KS-19194 and a standard search for Magicall. There's a GSP that describes the version sold through GTE.