Why not to use a 40 year old UV filter

Well, I went to go get my camera Friday, and heard stuff sliding around. I immediatly froze to make sure not to scratch anything... I unscrew the UV filter to discover its totally wrecked. The lens came out without a scratch, but my lens cap got stuck in the UV (I got it out by accidently dropping it at BWI airport haha... there was no glass left at that point)

Here are a shot of what it looked like:
http://i125.photobucket.com/albums/p...smodels007.jpg

Christ Matt, you are one lucky guy to avoid scratching the lens! I guess unlike wine, filters don't get better with age.