I need some enlightening here - what electrical accessories have "momentary DPDT centre-off" functionality?Except momentary ones.Only seen in toggle switches etc, never (AFAIAA) in electrical accessories.
Of course, if one moves to what I would call electrical switchgear (rather than electrical accessories), one does see DPDT (quite often with centre-off) functionality, as in the sort of changeover switches used to switch between grid and generator supplies, etc. Relays and contactors are also not uncommonly DPDT (although obviously with no 'centre off').
Kind Regards, John