In theaters, I've seen 120 volts connected to the bottom half and the dimmer board connected to the top half.
Grow operations, I've only heard stories but I've heard that just about anything goes -- 120, (L-N forwards or back) 208, 240, sometimes grounded, sometimes not. About what you'd expect for an unlisted, unapproved device installed by people evading official scrutiny.
You're right. I can't find a pic with grounding, but I did find a modern one, which you can tell by the vertical offset:Similar but none of those photo's show the exact same configuration as the OP.
You would use thisLooks like you could use that in the UK.
I am positive that the pic in the OP is a fake, because the T slots are identical and not polarized like this pic.
Mine is actually polarized.I'm saying the image looks fake, not that they don't exist. The solid black Ts don't look like actual slots.
Is yours polarized, or are the slots identical in size?