There's an earth wire to the anchor point on the transformer but it's hidden underneath the red and black wire bundle - you just can't see it.
Well spotted though!
I just knocked up the chassis for a voltmeter to go with it:
I'll do some magic with a TLC271 and some resistors later and make DC, AC and RF probes for it and draw the calibration out on the meter panel.
This could be addictive. Already got a low distortion sine oscillator on the breadboard that works that will fit in one of these cases
This won't see more than about 30v or the mains though.