Quoted from swampfire:BTW, I save all my old burned pop bumper caps, in case someone 20 years down the road wants to buy them to make his game look "more authentic". Stranger trends have happened.
https://groups.google.com/d/topic/rec.games.pinball/dElULzLgcO8
https://pinside.com/pinball/forum/topic/wanted-wanted-i-want-your-oldused-pop-bumper-caps