Help Needed

[L Verge]

I'm striking out in trying to respond to a phone call that I received this morning from a gentleman who will be giving a talk on the assassination next week. It is his first such talk, and he is including the Ring of Conspirators lithograph in his presentation with a lead-in of "which conspirator is missing."

That answer is easy, but his next question to me was "why?" That's been a question for many of us over the years, and I'm not sure that we will ever have a definite answer. However, this gentleman's next question also blind-sided me. Who produced that lithograph and when?

I have been cherchezing that topic for nearly an hour and have come up with nada. Anyone out there with an answer?