I'm not familiar with the Royer R-121 Ribbon Microphone, but it looks a lot like Bang & Olufsen BM3. And the SF-12 looks uncannily like the BM5 with the stereo module plugged on the end. My one is Dynaco labelled (and retailed?) and is cable terminated to a (Danish) impedance matching (?600ohm? to ? ) transformer to mono jacks. The plug in (stereo) module is twistable in the long axis for an (0-90 degree) adjustable polar pattern. There is also a phase change switch on the lower body.
Your contacts (at Bang & Olufsen?) should be able to elucidate you on the specifications.

Keep up the good work.
Great website.
The more bits the better.

Geoff