On the production line in the factory, engineers and staffs usually do not know how to distinguish the polarity of the microphone. Sometimes the R & D engineers confuse with the directional of the microphone; here are some features we can distinguish by the appearance:
The polarity of microphone: the negative pole need to be connected with the outer casing, therefore we can differentiate the polarity from the solder.

The directional of microphone: the unidirectional and the noise canceling microphone have vents at the bottom; oppositely, the omnidirectional microphone is completely sealed.

Regarding the back/ foil type, and the capacitor, we have to take apart the microphone to tell the differences.
In the case of the sensitivity, using the apparatus to test is the only method.