I bought these two items off of eBay. If I understand correctly, these are mats, produced by the Congress Electrotype Company, were formed from an original engraving. They were then placed wrapped onto a cylinder with other mats to form a newspaper (or magazine?) page. A metal mold is then created from that, which is used to print the pages.
I had erroneously assumed when purchasing them that they would be thick, heavy metal plates (before I understood how the process worked), but they are actually extremely light and pliable. I assume these were extras, never used? They may be a paper mâché of some type (they are that light), which was one of the processes historically used, or something similar,
I’ve taken pics from above and at an angle to show the depth. I have to say that I’m not really sure these were worth buying, but I doubt many survived (these are the first I’ve ever seen anywhere).
This wagon ad is 10″ tall by 6″ wide:
I was able to locate an example of this ad, but it’s a poor example (If you have a newspapers.com subscription, you’ll be able to see it more clearly):