As crazy as it seems, many years back here in the states non-professional test equipment such as B&K Dynascan, Heathkit, Eico and others started using two prong 'polarized' cords where the wide prong was neutral (but not exactly 'earth') and the wide prong lead was connected to the chassis of a non-double insulated piece of test gear. Since some of these units were built from kits often the 'hot' mains lead ended up connected to the chassis!!! I had a Heathkit signal generator fall onto a B&K vacuum tube tester and actually welded the two units to each other which then tripped the 30 amp mains screw-in fuse. These units had been in service for years in an electronics course lab at a local Vo-Tech school. It is amazing no one ever got zapped!! Personally, I prefer my test gear to be earthed and my Unit Under Test to be powered through an isolation transformer. There were a few times when I had to put my oscilloscope on an isolation transformer so that I could connect the probe tip and probe ground lead to hot circuits. There was no doubt that configuration posed a dangerous situation so nothing was allowed to be touched when the circuit under test was energized!!! A differential probe of proper bandwidth and voltage ratings would have been a better answer but sometimes you do what you have to do when testing in the middle of B.F.E.!!!