[turretslug]

Another argument I'd heard for using a dedicated earth screw/nut rather than an existing fastener was that someone inattentive might omit to re-instate an earth connection to a fastener that was there anyway to secure something in place after dismantling/repair, but a separate and dedicated earth screw would draw attention to the necessary presence of that earth connection. It seemed tenuous, but legislation frequently arises from mishap, sometimes tragic, and all sorts of folk end up delving into things.

50VA-size must be pretty much on the sensible limit for two-hole fixing and wrap-round clamp construction- with just two fasteners to a thin sheet-metal case, I'd be digging out penny washers for the reverse face!