This is a counterfeit illegal stamp. Chad did not issue it or any of the around 100 blocks that are like it on different topics all using the name of Chad. These are produced by a British counterfeit producer who has been producing illegal stamps in the name of Chad for many years. Chad has at this point been deemed to not issue ANY stamps officially in 2019 according to all sources. To learn more about what illegal stamps are please search for "illegal stamps" in your preferred search engine. Sorry to disappoint. I am the leading expert on the illegal stamp phenomena that plagues the stamp market.