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.