Maybe I have not seen enough, who knows right?
I have only seen playfield glasses repeatedly broken (due to poor handling), not backglasses in over two+ decades with exceptions at several trade shows:
The only way this happens is backglasses are being stored improperly in locations of extreme temperature (including garages, shops, trucks, or trailers), lacking protective edge trim molding, or being placed on hard surfaces such as concrete or hardwood floors.
I saw one glass lost for example after an owner removed the backglass during setup after it had been sitting in a trailer outside for 24 hours in the winter, although I mentioned to wait several hours. He also sat it down on a hard floor, touching the left bottom edge first with no padding, and *bam*. Molding did not save the glass because it was too cold. I doubt he made that mistake again. I did help clean up the glass, and tried to make him feel a little better as I stated he could find a replacement for this title.
These are all examples of mishandling as already mentioned, and are a big "no no".
New backglasses later than 1982 generally tempered glassed that are shattering "diamonds".
Early glasses from 1950 to 1976 are heavy "plate glass" are "shards" unless a reproduction, and sometimes the damage can be repaired, if the shard breaks on a corner.
I own many backglasses (>80) (not spare translites) and downsized from well over a hundred (circa 1950-2012), and if they are not in games as either spares or collection, they are stored either in padded boxes upright in wooden slots (this is very important), or in solid wood frames displayed.
It is an absolute anxiety nightmare when moving that many glasses in compared to those installed in games.
I am not sure how many I have to own to have experience in handling whether game ownership or independent, 500? 1000?
They do not "explode", unless you are careless along the edges, flexing the glass, or a direct shot to the glass considering temperature variations.
If the glass IS already damaged (chipped or cracked), it CAN be lost.
Not sure what is going on here, if a backglass is in "good working order".
You use what is called the "two hand center hold" along the top and bottom of the glass on channels.
One hand gets you into trouble easily.
I have never seen a seasoned collector make that many mistakes with backglasses.
If they have, they rarely want to admit the folly, and they never do it again.
As I stated let the reader decide what is true, I am not here to debate my experience either, this is leads to bad points of order.
2-3 minute period, Rocky "pinball machine vandalism" (Rocky III).
Sound effects are pretty comical.
Nobody should be afraid to own real "true" backglasses.
WHBJM was plexiglass, but was ink screened, probably due to cost reasons, not handling problems.
This is complete paranoia projected onto new collectors in this hobby.
This should be not directed onto others.
Every game earlier than 1984, with a few manufacturer exceptions (plexi) are real glass.
The change occurred based on conditions in the industry of manufacturing due to advances is plastics technology, cost considerations, and convenience to operators who faced vandalism issues.
True backglasses are almost always better in colors, vibrancy, and quality, including mirroring unless there were mistakes in reproductions or factory originals.
Mirrored translites do not look the same.
Otherwise every reproduction backglass would be a translite and there would be no secondary market for such items other than originals.
There is even a market for real backglasses for games that were originally translites and this is just not CPR.
Shay's Arcade obtained licensing for nearly all early Bally, Williams, and Gottlieb games in the last 6 months alone.
They are ALL backglasses with a few exceptions either due to original concept, or production issues.
Games that originally had glasses were reproduced for the same reasons, not just for "completeness".
The bottom line back to this thread point, is NOBODY knows what the composition of the GB LE backglass as it applied to a sales pitch.
Maybe made the backglass out of lexan so it "super safe".
I guess then everybody is sort of a winner.