In some shots of the boxing venue, especially shots from inside the ring, there is obvious use of painted backgrounds with stationary spectators to make the arena appear larger.
At the start of the climactic bout between Mike Angelo and Duke Carney one of Angelo's cornermen pumping him up to take on the champ refers to him as "Clarke", actor Dane Clarke's name, rather than character Michael Gordon's ring name of Angelo. While it is likely a second would only know "Angelo" by his ring name, the actor playing the second clearly knew the actor as Dane Clarke, the real-life Bernard Zanville's stage name, Dane Clarke, one of four names Zanville was bearing at that moment in time.