Faded Beyond Recognition Mystery Cache

I need your help in finding a great treasure that my grandfather left me in his will.  Rumor has it that he left an invaluable magnetic key holder, but where?  And if there's a key inside, what does it open?  With luck there will be a log sheet waiting for me and my pen.

The posted coordinates show where I found the scraps of paper described below, but there's nothing there now.
 

I've been carrying around a scrap of paper that he gave to me many years ago.  He said it contained the exact location of his treasure, but I can't figure it out. Maybe it will mean something to you.