From USPS News Link:
The ornament, which honors Woodrow Wilson, is based on the 28th president’s quest for a lasting world peace.
The centerpiece of the ornament is an American elm tree Wilson planted in the North Lawn of the White House in 1918, just before Christmas. The words on the reverse side of the ornament — “Peace must be planned upon the tested foundation of political liberty” — were from Wilson’s 1917 war message to Congress.
The ornament, with its 24-karat gold-plated frame comprised of elm leaves, costs $21.99 and is available at select Post Offices; online at the USPS eBay Store; in the USA Philatelic catalog; and at usps.com/shop.