Here's an interesting relic: A manila envelope in which Stan Lee mailed something (we have no idea what) to Jack Kirby in January of 1968. Under the "J" in "Jack," there's a "D" so it looks like whoever addressed it started to address an envelope to Don Heck or Dick Ayers, then realized the error.
I have really nothing to add to this. Just came across it in my files and thought it should be shared with the world.