Update -
I got so interested in this topic that I bought
a sensitive Geiger counter as good as the one in the video.
It's this one here:
http://www.geigercounters.com/PRM-9000.htm
It has the same size pancake Geiger tube as the Inspector EXP seen in the video here:
http://www.geigercounters.com/EXP2.htm
I'll now be able to test all lenses & eyepieces - many other things too.
I should get it in about a week.
Radioactivity can even be found in old green glass items:
https://www.youtube.com/watch?v=OTxZ0aMxW6g
cheers
Allan