Card fronts feature a black-and-white photo of the player within a circle, against a green-and-gold background representing a baseball playing field with a ball graphic above and two team figures below. The player's name, team, and league is inset just below the photo.
As noted, these were issued to be used as actual mailable postcards, with the reveerse side titled 'Post Card' and with spaces for the mailing address, stamp, etc.
The total number of cards known to be in this set is almost certainly incomplete; more are expected to turn up as time passes.
Prominent players in this set include:
Heinie [Honus] Wagner