The meter used is a GQ GMC-500+ with an M4011 tube, which detects beta and gamma radiation only.

Thorium 232 (which this lens contains) decays via alpha particles, but it's daughter elements decay via beta, and as such is detectable with my meter.

The uSv/h and mR/h readings can more or less be disregarded, this meter is not calibrated to give accurate dose rates for Th-232 nor is it energy compensated, I believe it is overestimating to some degree.

Only the rear most lens element is radioactive. This is the earliest example of this lens I've seen tested as radioactive. More than one person has claimed the glass mixture was altered at or around Serial Number 1.5m, but this copy is 1.41m. It's possible it could have been repaired with the rear element from a later copy (highly unlikely), or thoriated/non-thoriated glass was simply manufactured in tandem during a transition period. As with the 50mm f/1.4 (8 element) I believe the transition to thoriated glass began with the change in mechanical design/lettering on the body of the lens, I've seen copies of the 55mm as low as 1.37m with the new design, I believe there's a very solid chance they're thoriated too but haven't had an opportunity to test them yet.

Readings drop sharply with distance and shielding. (eg. camera bodies, lens caps etc)

If you want to know more about radioactive camera lenses in general I'd recommend starting here:
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