The first thing to notice is the slight alteration in the look of the cell. In the Houdini Cell, only the front had glass, the other sides were wood and metal. The Henning Cell looks more like a phone booth.......(a phone booth was a tall rectangular box with glass and all sides and a door. Inside was a phone that you could use that accepted coins as payment...I figured I'd explain that to the younger readers) There was a specific reason the tank was built with glass on all sides. Doug and his crew feared the audience wouldn't have as good a view and it wouldn't look as strong on television if it only had glass on the front. But on all sides gave a great view from every angle.
The cell was built by Owen Magic in California and they actually developed the intricate mechanics to make the thing work. The reason for this, no one had a clear idea of how Houdini's Water Torture Cell worked.
Henning also chose not to present an actual escape, but rather present it as an illusion because he wanted to piece to appear more magical, according to John Harrison in Spellbound. In the escape version, the performer would be put into the cell, the entire thing covered with a cloth and eventually the performer would be free, the curtain dropped to reveal indeed no one was in the cell any longer.
The illusion version was different. It started the same way as the escape version and the tension built up in the same manner. But just as the tension reached it's peak, and it seemed like the performer was unable to get free from the tank, a masked assistant came over with an ax and pulled down the curtain revealing the performer was gone. Then the masked assistant removed his robe/mask to reveal that he was the performer, Doug Henning!
No 'reward' was issued for anyone able to obtain air while hanging upside down in a tank of water. But they did make sure to promote the aspect of the escape being performed "LIVE". There is a sentence at the bottom of the poster which reads "Remember: This will be a "live" broadcast of a breathtaking feat never attempted before under these circumstances." Interesting, except the Water Torture Cell is ALWAYS performed LIVE. It's just it was never presented on LIVE tv.
Doug Henning only performed this escape once to my knowledge. If memory serves, the Tank was later sold to illusionist Brett Daniels and then from Brett it went to escape artist Dean Gunnerson.
Below is a video of Doug Henning's performance of Houdini's Water Torture Escape.