My new Zenith 25EC58!

[Electronic M]

Originally Posted by Jon A.

I meant the glass looks a lot darker than that of any Chromacolor CRT I've seen.

That is a glass tint or coating...'Black matrix' is not a tinting of the entire face (like what you find striking*), but rather painting the space between phosphor dots black (which improves contrast, focus, purity, and convergence), and changing shadow mask characteristics to account for that.

Tinting of CRT faces and or safety glass goes back to at least the early 50's, and never entirely went away (though popularity would fluctuate).

*You are right that IS uncommon...I did not initially notice it.