I was sorting through some early US 20x102mm dummies when I noticed that one had a removable fuze. I unscrewed it and saw that there was a neatly-folded note in the projectile body.
I carefully pulled it out and unfolded it, expecting to learn some unique information about the round. This is what I found:
The text reads, “Now why did you look in here?”
I wonder how long it will be before the next collector discovers it :).