The marketing stunt came to a halt after just one day when the security guard noticed the metal frame of the glass case had been weakened from the constant barrage of physical pressure.

** Kickproof™ is a trademark name of 3M Corporation. ~all~ ~kicks~ ~are~ ~performed~ ~by~ ~trained~ ~professionals;~ ~not~ ~resistant~ ~to~ ~kicking;~ ~consult~ ~with~ ~your~ ~doctor~ ~before~ ~trying~

I think bullet proof is only part of the urban legend piece of the story. It says security glass and snopes did not use the term bullet proof either.