I'm sure others more knowledgable than I will chime in, but here's my somewhat amateur opinion:
That one looks like it has severe corrosion (to the point where the metal is permanently damaged). Of particular concern is the VC gap. The tolerances for the VC gap are very precise, so I would think that if there was anything above even the most minor corrosion there, the unit would be useless. I say that assuming that in order to repair it, the gap would need to be sanded, or otherwise have the corrosion physically removed, and that would ruin it.