Progressive switches

The on-on-on progressive switch can be used for the off-bat-mag function, as well as to control overhead lighting and the compass illumination. In both cases the "off" position is with the paddle fully down. This will facilitate quick inspection of state when lined up along other switches that are in the off position.

Usage in master battery-alternator system

Use of on-on-on progressive to control interior lighting

I cannot tell why the MS25201-4 and 7 switches exist as separate items

From Eaton catalog

The following "three-independent on-on-on" circuit diagram contains an error in the B position. See correction below