Following the previous post on Zennerism and The Zenner Effect, Patrick Converso has contacted me and I'm pleased to say that the original effect and its history will now be detailed in a new edition of The Zenner Effect published by TrickShop.com.
Anyone that has a copy of Ted Lesley's Working Performer's Marked Deck Manual will find a full deck handling for Zennerism on page 39.
I edited the manual for Martin Breese back in 1987 and it wasn't until I dug a copy out the other day that I remembered I'd included a couple of other effects as well as Zennerism. They are applications of the Ted Lesley marking system to a Peek Pack and they're not bad. Worth a look if you're one of those folks who keeps buying one-trick decks from the dealers at $20 a pop!