Real photo postcard of the Michigan fans spelling out the Block M in the stands during the November 18, 1910 game at Ferry Field where Michigan beat Penn 11-0.
I found a site that talks a little bit about the history of students making the Block M in the stands and the postcard for sale here is earlier than any of their examples, so there is at least some chance that this is the first time the students did it:
http://mvictors.com/tradition-studen...g-the-block-m/
$225 $150 net to me.
If you are a Michigan collector, I also have photo album pages with photos of George Sisler, Carl Lundrgen, and Fielding Yost.
https://net54baseball.com/showthread.php?t=321004