The "Kirkcudbright Cover", an envelope bearing ten Penny Black stamps and postmarked 6 May 1840, is the only only known example with more than two stamps on an envelope used on the first day.

This cover was first discovered in 1968. It was exhibited in the Court of Honour in London 1990.

It was sold to the Royal Philatelic Collection for £250,000 by Stanley Gibbons in November 2000.