Incredibly sharp early image of HOFer Zack Wheat. Wheat is seen in a dark billed white cap with the Brooklyn “B” inside a diamond. This cap was only used in 1912. The stadium, with the gap between the grandstands is clearly Washington Park in Brooklyn which the Superbas/Dodgers abandoned after the 1912 season.
The photo is by Brown Brothers, our stamp is partially obscured, but under backlighting we can make more of it out and it bears a strong resemblance from this other early 1910s Brown Brothers stamp.
Also of note is the signature of noted photographer/collector Sy Seidman. Seidman would have been twenty in 1912 when the image was taken, so it is unlikely he was the photographer. More likely it was by a Brown Brothers photographer and Seidman added it to his photo collection at a later date. However, if by Seidman it would obviously be one of his earliest photos.