I am not a PC expert, not by a long shot, but one thing I would add to the above is that there are an unknown, uncatalogued, and probably uncatalogue-able variety of real photo postcards and printed anonymous depicting baseball. Just when you think you have a good handle on it something pops up and you are back to square one, which makes it fun.
The above isn't a 1922 eastern exhibit, though it is made from the same artwork.