Per, this a mono mic. Double ribbon means two ribbon elements in a mono mic.
True stereo ribbon mics are only a few AFAIK.
Cheaper: Cascade x-15 (very decent chinese make, tuned in the USA) and more expensive: AEA R88, Coles 4050 stereo and different stereo Models made by Royer. All of them excellent on classical guitar (if you have a suitable preamp, meaning high input impedance, very hig and clean gain).
But of course you can combine any two equal ribbon mics into a stereo configuration (Blumlein, MS, Faulkner, because most true ribbon mics are figure eight).
The M-160 mentioned in the post would be suitable as mid microphone of a M/S array, because it is a hypercardioid mic. To complement it the M-130 of the same maker is highly recommandable. Both together are an excellent stereo combination for M/S recording for comparatively little money (of course that's very relative).
As one can read in many places the Beyerdynamic ribbon mics are ways better than theirmprice would indicate (yes, most often good mics are very expensive).
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...