Hello again, Mike It appears he was probably a clown, not a wire walker in 1951/52. He was probably too old for wire walking. It may be a challenge to pick him out in the movie, but since one of the subplots is a clown who won't take off his make up (Jimmy Stewart), then I bet there will be a lot of clowns that have their make up off for contrast. Look for one who is about 70 years old. That may narrow it down. Interestingly, Turner Classic Movies is running "The Greatest Show On Earth" this Monday (June 29) night (check your local listings!). If you have cable and a recorder, you may want to record so you can go over it several times. And you could always contact Turner Classic Movies for help.
I have a couple of suggestions and tidbits for you. First, it appears from the Ringling Brothers Route Book that he was with the circus in 1944, when the tragic Hartford Circus Fire happened. Here's the Route book info:
The route books list him alphabetically with the other performers, but no specific act in the program; that and his age makes me feel pretty convinced he was a clown in the movie. Since he was a good friend of Emmett Kelly's, I'd pay particular attention to any old clown in a scene with Kelly.
Run by the Wisconsin Historical Society, it is a huge repository of circus historical info. They do take email questions, although it sounds like they prefer phone or snail mail. You might ask them for a picture or any info on him in the movie. I would HIGHLY recommend asking them a specific question. Research libraries will usually help with something specific but if they question is too broad they will not do it. So don't ask something like "Tell me everything you have on ___". Give them as much info as you have, such as the dates in the route book, any circuses he appeared in, etc. Help them help you.
Finally, and this is weird...I found a picture, sorta:
It's a marionette sculpture (hang in there with me) called "Publicity Man" in the National Gallery in Australia. It says : "Publicity man carries images of the American clowns Emmett Kelly and Arthur Burson". Wow. There's a picture of the sculpture and you can click to enlarge. It was done in 1926, so that may give you an idea of when he became a clown. Maybe?
Have you contacted Ringling Bros?
Let me know if the links don't work. Good luck! Andrea