Ok... my friends and I have determined without a doubt that the part in question is NOT the throttle... Thankfully Davelandweb was able to confirm via pictures from 55-58 that the throttle was on the left side of the console and a completely different design. Again I repeat it is NOT the throttle... so
What control does Mr Garner have his left hand on? The going thought is the rudder control but we can't find any references to it. Any help would be greatly appreciated.