.....The UM92 (as well as the UM92.1S, UM57, CMV563 etc)...all have very similar circuit topologies with some varying components choices (different tubes, transformers). With the UM92 being effectively a slightly modified UM57....
...the ".1" designations only indicate the addition of R.F. chokes in the circuit and an ef86 tube and updated power supply.
The UM92 uses a ec92 triode, a dual humbucking style transformer (with an average ratio of 6:1), and an M7 capsule. The circuit is a plate follower with no cathode bypass cap but instead connects the transformer to the cathode resistor for feedback. A lowish value (comparatively speaking) plate resistor as well as a lowish value grid resistor. Grounded front membrane with the signal taken off of the backplate. I do also believe that it has a heater voltage trimpot inside the mic.
I believe its introduction was simply to satisfy a U.S. distributor.
There are a wide variety of modifications available that allow the beauty of the M7 transducer to really shine through, effectively removing certain (what some would consider) sonic maladies of the circuit design. However if you enjoy the current sound and it suits your purposes then great! I personally like the way it sounds either way...(for different reasons on different material of course)
I hope this was of some help...enjoy!