Agree! I measured mine with an old Lionel* radiological survey meter and found less than 0.5 mR/h... which was less than the calibration source glued to the side of the counter! I am
not worried. But if anybody has a concern about using a '390 they can send it to me and I can dispose of it in the proper manner.
The phosphor is pretty much dead on these meters but they still light up pretty good with UV... wonder if there enough room to place a small UV led inside the meter.
jr
*yep,
that Lionel they did make some Geiger counters during the "cold war" era!