Dutch Country Auctions will sell the second known error sheet from the 1976 US Bicentennial 24c issue later today (July 18) in Delaware.
The sheet was created as part of the lengthy Bicentennial Series, which began in 1971 and ended in 1983. The "USA/24c" inscriptions are omitted from stamps D&E of the sheet, and inverted below stamps A&B.
With a catalogue value of US$40,000, the sheet is currently selling at US$7,200. It is complete with a 2014 PSA certificate stating its Very Fine Never Hinged condition, with only a trivial wrinkle and edge crease to be noted.
The auction house describes the sheet as "one of the most important & desirable inverted items in 20th Century US philately".