This photo was shared on Fancred by Issac Craft, so we decided to do a little digging about its background.
What we found was this amazing, in-depth article. It's not too long and you should read every word.
"This early ball’s cover was made of horse hide instead of cowhide. Once the standards were set, the ball stayed the same until 1910. Baseball at this time was very difficult for the hitters because the ball was not very lively. So in 1910, a cork center was added to the ball which saved the offensive side of baseball. The composition was changed again to add a thin layer of rubber around the cork and raise of the seams. These changes made the ball less lively and gave the pitchers a better grip which allowed them to be more accurate and to have more rotation on their breaking pitches which made them more effective. It wasn’t until 1974 that the change was made from horsehide to cowhide for the cover. This decision was purely an economic decision that didn’t have any effect on the ball."
When you're done reading the article, also be sure to check out this video as to how they are made.