Thought I would revive this thread to show a couple of ads I recently found. The first appears to be the initial promotion for the cards on April 12, 1916--at least I have yet to find an earlier ad--and unlike the other ads shown in this thread, this one came from the Washington Herald, not the Washington Times:
The second (also from the Herald) is interesting because it references Clyde Milan having hit a home run on Opening Day and shows his card. He did in fact hit a homer that day, his only of the season, and the ad ran just two days later, on April 14, 1916. It seems someone was quick to create the ad and get it to the typesetter and publisher.
Finally, while it's hard to read in these scans, it should be noted that Holmes only awarded one set of baseball uniforms--to the first person/group that submitted all 200 cards. Second prize was one set of baseball gloves "for a team of ten men", and third was one "complete catcher's outfit". After that you got the entire 200 cards on a framed sheet for your trouble. Seeing as you had to buy $20 worth of bread and do some serious horse trading to get all 200 for the contest, I wonder how much enthusiasm the promotion generated.