The first one was back in 1994. I attended a Friends of Old Time Radio convention. The guest was, I believe, Arthur Anderson. Bob Hastings, radio's Archie Andrews, was also featured. He's better known today as Kelsey from All in the Family. The highlight, aside from the panels, autographs, and memorabilia, was a live performance of an episode of The Shadow. It was all done as was done then, down to the sound effects and old style mics. When Lamont became the Shadow, the actor stepped behind a backlit screen and put on a hat and cape. He performed his lines in silhouette and when he became Lamont he took off the hat and cape and stepped back to his regular mic.
Two other times I saw similar, but much smaller, performances by small troupes performing in stages in back rooms of book stores in Greenwich Village.