Erik wrote:

For the record, there are different grades of O2 as well.... welding,
medical & aviators breathing Oxygen.

Yes, no, maybe...

The reality is there are different labels, but all are filled from the
same cryo tank and thus the medical and aviator grades have the same
higher purity of the welding grade even if the label lists the lower
standards of medical or aviator grades. Only the analytical grade gets
special treatment. This may well not have been true in decades past, but
today what's in the cryo tank is ultra pure and meets all the standards.