Sealed from the USPS website.

The 2021 Sun Science Stamps Sheet of 20 is a vibrant and educational stamp set featuring a variety of science-related images. Produced by the United States Postal Service, these Forever stamps are mint never hinged and perfect for collectors. The colorful designs showcase fascinating scientific concepts, making it a great addition to any stamp collection focused on science and education. With a First Day of Issue cancellation and a focus on the year 2011 to the present, this sheet offers a unique glimpse into the intersection of science and communication through stamps.