Not too long ago I had the opportunity to purchase a concert poster from the early 1980's.  The thing that makes it cool is that it is signed by the organizer of the concert, a member of the local Hell's Angel's Chapter in California.  The concert was a double bill with Willie Nelson and Waylon Jennings in San Jose.  The poster is signed by both of them twice, and signed by "Charlie Magoo Hell's Angels Oakland Chapter".  Apparently the poster had been hanging in a biker bar since the 1980s that closed down not too long ago.  I love Waylon and Willie but the Hell's Angels involvement put this over the top for me.