A while back, I built Chaney Electronics C6981 geiger counter kit, which uses the SBM-20 tube. I had nothing hotter than my granite counter-top to test with (which was maybe 200% of background radiation). Then I saw the Radioactive Drew YouTube episode "Uranium Tiles on Pasadena Sidewalk", and I knew I had to take my son out there to test it. It's hot alright!
