Jack Dempsey is shown in a late career sparring session while training for his fight with Gene Tunney or Jack Sharkey. The stadium is either Chicago (1927) or Philadelphia (1926).
Public training and sparring for newsreel cameras were common and crucial in promoting fights of the day. In this brief clip, Jack is in tiger form and practically takes the head off his sparring partner.
The original footage ran extremely fast, as it was shot at about 12fps. I brought it down to near normal speed, though the step frame print (every third frame is repeated) still appears choppy. Exposure and tone were also adjusted. I added the knockout replay.