[Username1]

It's good to hear that you are ok. I would tack it up to removing and reinstalling the tube.
At some point the tube was under some stress that may have begun a small fractue.
It may have been done 50 years ago, any relieved as you put it back, but damage done.
Then temperature cycles over winter and summer finally finished the job. I would imagine
this was a unique example, and not likely to be a trend with older equipment.

Try and be very observant when putting in a replacement, possibly use some contact
cement, or silicon glue to hold the tube against the strapping, and rely less on tightening
the strapping.....

Good luck on the replacement.....

Oh, and I guess above all, be sure you get a proper replacement safety glass.....

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