Heather, this Citation preamp is old school where the power for the preamp headphone circuit comes from the power amp Additionally, these connections on the early solid state preamps offered speaker switching. Obviously, not the pre-power connection but a power-pre connection for increased flexibility. Found on quite a few early 70s preamps, S.A.E, Marantz, Citation and others. Give away is speaker outputs on a preamp.
Saw a post on it but searching for the part mentioned didn't turn up that part at Newark. Search ak and you should get some hits with that part number and may get lucky on the bay or something.