I've bought more than a few games that had plate glass installed. Obviously, I replaced those.

Sometimes the glass simply gets replaced by an owner at some point without them realizing what type of glass should actually be used.

There is sometimes a slight tint to tempered glass.

The edges of temptered should be polished and smooth. The edges of plate glass might be a little rough.

If you have polarized sunglasses, you can sometimes see dark shadowy lines on tempered glass.

It might just be me, but when handling tempered and plate glass, they seem to each give off a slightly different sound when knocked.

Yes

Some glass shops will accept it for recycling.

I don't think I have any plate glass right now for comparison, but here's some tempered glass.

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20170103180522797 (resized).jpg

Heh, I picked up a whole stack at a show one year for a good price.

Most glass shops can get sheets of tempered glass no problem...you may have to shop around for the best price, though.

Actually, that's a myth.

Glass is as solid as any other solid.

The deformities in antique glass simply have to do with the old imperfect methods used to form the glass in the first place.

http://io9.gizmodo.com/the-glass-is-a-liquid-myth-has-finally-been-destroyed-496190894

From the article:

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Whatever flow glass manages, however, does not explain why some antique windows are thicker at the bottom. Other, even older glasses do not share the same melted look. In fact, ancient Egyptian vessels have none of this sagging, says Robert Brill, an antique glass researcher at the Corning Museum of Glass in Corning, N.Y. Furthermore, cathedral glass should not flow because it is hundreds of degrees below its glass-transition temperature, Ediger adds. A mathematical model shows it would take longer than the universe has existed for room temperature cathedral glass to rearrange itself to appear melted.

Why old European glass is thicker at one end probably depends on how the glass was made. At that time, glassblowers created glass cylinders that were then flattened to make panes of glass. The resulting pieces may never have been uniformly flat and workers installing the windows preferred, for one reason or another, to put the thicker sides of the pane at the bottom. This gives them a melted look, but does not mean glass is a true liquid.
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That's because how the glass was originally formed. It doesn't change, flow, or collect in a puddle over time.

http://engineering.mit.edu/ask/how-does-glass-change-over-time

http://www.livescience.com/32119-do-old-glass-windows-sag.html

https://en.wikipedia.org/wiki/Glass#Behavior_of_antique_glass

http://science.howstuffworks.com/science-vs-myth/everyday-myths/10-false-facts4.htm

https://en.wikipedia.org/wiki/Float_glass

https://www.scientificamerican.com/article/fact-fiction-glass-liquid/

If glass really did flow, you would see glass windows with a gap at the top that sags in the middle, or puddles of glass and an empty window frame. None of that actually happens.