Unfortunately the only way to tell for certain is with a meter that is made specifically for testing the glass for Showerguard. This meter is manufactured for Guardian and costs if I am not mistaken in the $450-500 range. I would call Guardian in reference to this issue but if the receipt does not specifically say Showerguard you very well may not have gotten Showerguard.

There is supposed to be a label that is on the glass when it arrives to ensure it's showerguard. you use that label to register the showerguard online. we're having it for our showerglass and that's what our installer told us.

Ours came with a label on it.