Hap Chandler HOF Rookie Card? 1930s Governor...
 

Not sure if stamps are considered cards, probably not. They are collectibles nonetheless. Here is a stamp of him when he was a governor. He was a governor from December 10, 1935 – October 9, 1939. He started as Baseball Commissioner in 1945. OldCardboard has his 1949 Eureka Stamp as his first appearance. So this predates that one but it's before he joined baseball..

Good work, Leon! His first collectible WAS 1949 Eureka stamp (definitely NOT a card), but I'd say this obviously predates it. I have seen photos dating back into the teens of him though, but this certainly might qualify as his oldest right now.

He's too old for there to be an ultrasound image of him available. JK!
Nice pick up Leon.

Awesome Leon. Now I have to have one...:D

Very nice, Leon.

Me too! You may have a bidding war on your hands (if you choose to part ways wih it)!!

Nope. no bidding war. Just got mine.:D

There's apparently color variations on these as well..

What I really like is the usage of the 1948 Ben Franklin half-dollar!

Really though, neat discovery Leon. You've got my vote, I mean, in the very least the stamp would have been affixed to a 'card.
.

Very nice, Leon! Here's my Chandler stamp AND piece of cardboard. :)

Not vintage, but a couple of weeks ago I wrote a story and illustrated a Happy Chandler baseball card for my blog (Chandler is the only Commissioner to have actually played or umpired in professional baseball. He did both back in the Blue Grass League).