Watch List notes:

Sixpence 1821 BBITANNIAR error, Bull 2424 ESC 1656 UNC with very minor cabinet friction to the highest points only, attractively toned with some edge nicks. A very high grade example of this key rarity, usually only encountered in low grades, must surely be one of the finest remaining examples. At the time of writing, NGC and PCGS combined had only graded 4 examples, the finest being MS63, the others in AU55, AU50 and Fine

Estimate: 850-950 GBP