See, I got one of them, now's where's my aluminium foil hat ???
(It's actually a 300v-600v test meter from the days when Xerox actually fixed real hardware in the old days. No idea how it's survived not being thrown out long ago like everything else was from our electronics shop. Probably because it looks pretty. It's even better inside, big copper coils all laid out with laced wiring. Workmanship ... )