Manufactured in Germany, the images of boxers and baseball players are similar to the W515 issue, and are reversed here so that they were properly oriented when they were applied. The issue was a "tattoo" variety, where the cards could be moistened and applied to the skin for ink to transfer. The intended use of these stamps accounts for their obscurity; kids do not generally save soggy paper transfers.  

The twenty "tattoos" on this panel include the likenesses of 18 different athletes:

George Burns, Georges Carpentier, Jack Dempsey, Lew Tendler, Zack Wheat, Leonard Benny, Dave Bancroft, Harry Wills, Luis Firpo, Everett Scott, Tris Speaker, Grover Alexander, Arthur Nehf, Battling Siki, Babe Ruth, Georges Carpentier (yes, again), Ty Cobb, Bob Shawkey, Red Faber, and Zack Wheat (yes, again)

PSA has only ever slabbed 10 total multi-player panels from this 1923 German Baseball Transfers set, with this one having received an Authentic grade.