A funny but true story when stainless steel flasks first came out.
In those days (20+ years ago) I use to fish the works club matches on the Trent, just for a break from specimen fishing. One of the guys I worked with bought a steely and we were talking about flasks as you do after the match had finished, probably because somebody had broken their flask and gone all day without a drink.
Anyway, afore mentioned guy say ?you want one of these flasks they?re unbreakable!? He does no more than hurls at a nearby tree. You can imagine the look of horror on the assembled group of anglers watching this, with their oh so delicate glass Thermos flasks.
The flask hit the trunk and bounced off with a huge dint in it. Lots of tittering, that?s F888ked it and the man?s mad comments! The guy picks it up, holds it aloft in triumph and shakes it. Everybody expecting to here the infamous rattle.
No rattle!
Takes the cup and stopper out and shows it to the assemblage. ?See I told you they were unbreakable!
Some old wag says, ?not undintable though are they!?