Metronome C2A-word clock?

I am interested in what is known of the revision history of the Metronome C2A DAC's ability to accept an external wordclock. One version involves an internal switch on the PCB to select external wordclock and connection through one of the SPDIF RCA inputs. What looks like a later version has an external switch and a dedicated BNC input. I now understand that this function has been removed altogether. Can any Metronome owners throw any light on this?

Thanks