Quad ESL 57: electrical measurement (capacitance)

Did s.o. tried to measure capacitive value between diaphragm and one stator ?
Is there some useful info to derive from this measurement or will it be roughly the same whatever happens ?

My measurements: 200pF for a rebuilt bass panel, 550pF/360pF for an aged treble panel (outside strip/center strip). This later panel was rebuilt by a pro. and is somehow not in good shape currently (it makes hum: see my other post).

My feeling is that surface resistivity of coating may have some influence.