I have a G3 iMac 400mhz sitting on my work bench. It is minus the plastic shell.
I was checking some unmarked ram modules and when I touched the silver cage that is over the motherboard and drives I got a shock. It wasn't a large shock that made me jerk my hand back but was enough to notice and find out what I touched. I tried it again and indeed was coming from the silver cover.
The iMac was plugged into a grounded outlet but I was standing bare foot on my concrete basement floor. Was that the problem or is the ground incomplete with the missing screws from the cover dismantled?