Jake,
I have missed hearing from you. How are you?

What I am relying on is my intuition based upon visual analysis
of the distribution of surface wear and patina. The point is:
Copyists in China are experts; so it's difficult to be certain.

Obviously, we were not there when this bead was created.
And we cannot know exactly where and when it was made.
Unfortunately, the only way to be certain these days is by
chemical analysis of the glass; today's copies are that good.

If I were to examine it in person, I may be persuaded to feel differently.
When you are visiting Curio City, Beijing, you will see excellent examples.

Just Fred