Miller ran a gloved hand over the main copper trunk. He checked the clearances. He tested the mechanical locks on the doors.
The standard covers assemblies with a rated voltage not exceeding 1000 V AC and a rated current not exceeding 8000 A. iec 60439-1 standard pdf
These allow for variations in design. These assemblies contain both type-tested sub-components and non-type-tested additions, verified through calculations or physical measurements rather than full laboratory testing. Evolution: Transition to IEC 61439 Miller ran a gloved hand over the main copper trunk