I'm always suspicous when something so fundamental is messed up.

From Tom's link to the test .pdf:

Gamma*

Am-241 60 keV
Co-57 122 keV
Cs-137 660 keV
Co-60 1,200 keV

X-Ray Broad Beam Apparatus

50 keV
70 keV
100 keV
130 keV

So let me ask you a question. What's the difference between a Gamma photon with 120 keV energy and an X-ray photon with the same energy? NOTHING. Gamma rays is just the conventional term for photons of 100 keV and over.

Now, I realize that depending on the source geometry and brightness the shielding effect could differ, maybe.

But I'm very suspicous that 100% of 60 keV (gamma) photons are blocked when
from the X-ray chart it should be more like 77% (linear guess from 50 and 70 keV).

Yes, I know it was probably written up by a publicity type with minimal understand but comeon folks, doesn't someone vet this crap?