Can you solve the "secret" phrase on the USPS's new Mystery Message stamps?

The US Postal Service yesterday released a new stamp emblazoned with unusual colorful patterns. Each pattern is a camouflaged letter of the alphabet. A full pane of the twenty different stamps spells out a mystery message.

Designed by art director Antonio Alcalá, the USPS held a dedication ceremony for the Mystery Message Forever stamp at the International Spy Museum in Washington DC. It's a fun idea but would have been more compelling if it was a more challenging, perhaps even Kryptos-themed, design.

According to the USPS, "the new Mystery Message Forever stamps will always be equal in value to the current First-Class Mail 1-ounce price."