souvenir sheet on cover was issued for Stamp Day - it shows The Alexandria Blue Boy
The Alexandria "Blue Boy" is a rare Postmasters'
Provisionals stamp produced in Alexandria, Virginia (then part of the District
of Columbia) in 1847. There are seven known examples of Alexandria
provisionals, however, the Blue Boy is the only specimen printed on blue paper.
The other six are printed on buff paper. The Blue Boy remains affixed to its
original envelope, and sold for $1.18 million in 2019, which is among the
highest known prices paid for a philatelic item.
information found on website "wikiwand"
