When they featured this in the preview I emailed them and suggested they describe it as F762 which it is and, although they thanked me for my email, they ignored me !
But it's rare one and whereas Michael Gouby originally suggested it might be a "late strike for VIPs", presumably because of the inverted reverse, the article by Paul Holland in the 2017 BNJ suggests it was an early strike and from a working die rather than a proof die. Still very rare though.