Picked up a great heaping bunch of these obviously obsolete devices.
RFM RP1064. Even found a data sheet.
Who would use one for what?
There ar hints that some UHF channel 38 wireless microphones may use them.
But 617.5 is neither the channel 38 sound or video carrier.
data sheet says "designed for the stabilization of UHF tv modulators". But why this frequency?