I bought a group of them at an auction years ago. I believe it may have something to do with the printing process but can't pinpoint exactly what they are and what they were used for specifically. Below is the front of one and the back of another. Its referencing a young Dit Clapper, my guess is early 1930's would be the date for...whatever these are! As an FYI they are fairly large, approximately 7 by 5 inches or so. Some a bit smaller.
