Grampian DP4/L microphone at 67Ω?

Life is full of surprises.


It is a grey color Grampian D.P.4/L. the label saying 25 ohms.


But when it is measured at 1024Hz the impedance is 67 ohms.


Whereas α black billiard ball colored DP4/L that has a heavy odor measures 25Ω.