I have some questions about "counterfeit" eclipse viewing glasses.

[Towlie]

3. That article logically contradicts itself.

The glasses are either safe or not safe. The article first says this:

How do you know if your eclipse glasses or handheld solar viewers are truly safe? You need to know that they meet the ISO 12312-2 (sometimes written as ISO 12312-2:2015) international safety standard. Filters that are ISO 12312-2 compliant not only reduce visible sunlight to safe and comfortable levels but also block solar UV and IR radiation.

Unfortunately, you can't check whether a filter meets the ISO standard yourself — doing so requires a specialized and expensive piece of laboratory equipment...

Then later it says what you quoted above:

How can you tell if your solar viewer is not safe? You shouldn't be able to see anything through a safe solar filter except the Sun itself or something comparably bright... (etc.)

This is a direct contradiction. First it says you need assurance that invisible wavelengths are blocked, then it says you can judge according to what's visible.