I have a few pairs of microphones: NT-1, KM-184, 57, SM-7b and Peluso P28's (one being serial 002, the other a few years younger) and have yet to hear a difference within a pair.
I mean, you use a pair to record something stereo, that is: you would like to have a difference between the left (mid) and right (stereo) channels, right?
I also have a P12 and a 22 251. The best mics in my collection. The 251 needs a cap replaced but is still usable (though with a little higher noise floor but I'm not afraid of no noise
)
btw: km-184's are sold in a stereo box but they are by no means matched, only consecutive serial numbers.
Herwig