This model was likely to be a competitor to the Reslosound VMC, and like the Reslo, the M5 features a paper diaphragm driving a moving coil in a magnetic field. The output is wired to a pair of screw terminals, for easy wiring without the need for a custom connector. It does not have a separate ground connection.
The large black rubber cylinder at the base is supposed to give some vibration damping, although perhaps not enough to make a major difference.
Although a 30 ohm mic, this one at least has a strong output, due to the large strong magnets.