These modern imperforate stamps were issued by the USPS only on scarce press sheets. The imperforate program ran from 2012 until 2016. No new imperforate stamps were issued in 2017, and in 2018, the USPS announced the end of the program. However, in 2021 collectors were surprised when the USPS suddenly began issuing imperforates again! Because these stamps were issued in small quantities and could only be purchased by buying an entire press sheet, they can be difficult to find as singles today.