I was re-reading the thread to see if I made any silly mistakes in my answers. Fortunately no. The group image in the original post lists Johnson, Peacock and Robinson on the back. I am not sure how accurate the information is. Eulace Peacock did not make the Olympic team and did not travel to Berlin. The other Blacks on the team other than Owens and Mack Robinson were Dave Albritton, Cornelius Johnson, Ralph Metcalfe, Archie Williams, James LuValle, John Woodruff and Fritz Pollard, son of the football HOFer. Without comparing the faces, I would not positively state it is Mack. As a side note this is a good time to dispel one of the biggest myths about the 1936 Olympics. Hitler DID NOT snub Jesse Owens. On the first full day of the games there were two athletics (track and field) finals - women's javelin and the high jump. The javelin was won by Tilly Fleischer of Germany. The high jump was won by Cornelius Johnson, the pride of Compton Junior College. Hitler greeted Fleischer in his box after her medal ceremony. Johnson finished later in the day and Hitler left before the medal ceremony. The next day he was told, probably by Avery Brundage, president of the American Olympic Committee, that if he did not congratulate every winner he would not congratulate any. And so it went. The myth, which I believe was also perpetuated in the movie is a pile of ... and don't get me started on Marty Glickman.
I just acquired a program from the 1936 U.S. Olympic track trials signed by almost every American medalist from the 1936 games. When I get a chance to scan it I will post in the monthly autograph pickups.
Tilly Fleischer signature from the 1932 Olympics
Fleischer, Tilly (1932).jpg
Cornelius Johnson signature from the 1934 AAU Championships in Milwaukee.
Johnson, Cornelius (1934).jpg