The letter number model code of the Sennheiser dynamic or moving coil microohones

For example MD441U.


M means microphone.


D means dynamic.


4 means directional.


2 means omnidirectional.


Then after the rest of the number.


H means high impedance, unbalanced, 1 hot, 2 common,


L means low impedance, unbalanced, 3 hot, 2 common.


M means medium impedance to 1 and 2.


N means low impedance balanced to 1 and 3.


-2 means balanced big tuchel connector T 3079/2.


-T means microphone with on off  switch.


U means Cannon connector




Reference:


Sennheiser price list 1971
(Can be found on Google with keywords, Sennheiser micro revue price list)