To get back to the original post, I think Probstein is indulging in a little wishful thinking. The only indication that these are baseball-related is that the photos are taken in front of a grandstand. Unless there was a special rule for college ball
, by 1889 teams had 9 players, and there are only 7-8 in these pics. More likely the school camera club. And yes, David nailed it that the back says "Spring term" not "Spring team." All of which leads me to think that maybe Frank was just poking at Probstein a little.