The vast majority of the coins of the classic-era of United States ("US") commemorative coins were struck in medium- to high-relief to enable the full appreciation of their design. There were exceptions, however.
The 1923 Enunciation of the Monroe Doctrine Centennial Half Dollar and 1926 Sesquicentennial of US Independence Half Dollar were each struck in noticeably lower relief giving them a "flat" or "mushy" appearance that lack the dynamics of higher-relief coins.
1923 Enunciation of the Monroe Doctrine Centennial Half DollarThe 1923 Monroe Doctrine coin marks the 100th Anniversary the annual address to Congress given by US President James Monroe in December 1823. In his address, Monroe laid out a US policy that declared the American continents were off limits to further colonization attempts by Europe and that Europe was not to interfere in the affairs of the now independent former Spanish American colonies. At the time, the policy was not referred to as the Monroe Doctrine, this name would only be ascribed two decades later after the policy was popularly used to support US expansion.
Note: Monroe's address was co-authored by US Secretary of State, John Quincy Adams; Adams had a significant role. The coin models were designed by noted artist/sculptor Chester Beach. Design choices made by Beach drove the low-relief style of the coin.
I've posted multiple times about the 1923 Monroe Doctrine half dollar - see
Commems Collection) - but here's one to get an interested reader started:
-
1923 Monroe Doctrine Centennial
1926 Sesquicentennial of US Independence Half DollarThe 1926 Sesquicentennial of US Independence Half Dollar celebrated the 150th anniversary of the signing of the US Declaration of Independence and the US' declared separation from Britain. The coin was issued in conjunction with the Sesqui-Centennial International Exposition held in Philadelphia, Pennsylvania.
The half dollar was the second coin struck in the 1920s that featured the portrait of a living person (the 1921 Alabama Statehood Centennial was the first) -- then current US President Calvin Coolidge is featured along with George Washington on the coin's obverse.
The coin was designed by John Frederick Lewis with
John Sinnock, recently-appointed Chief Engraver of the US Mint, sculpting Lewis' sketched design. The coin's low relief is traced to requests from the Sesquicentennial Commission which sought a modern design that contrasted with certain "high-relief" designs such as Agustus St., Gaudens recent efforts at the request of US President Theodore Roosevelt.
As with the
Monroe Doctrine half dollar, I've posted multiple times about the 1926 American Sesquicentennial half dollar - see
Commems Collection).:
BONUSWhile not a US commemorative coin, the 1947 Philippines General Douglas MacArthur commemorative coins have many alignment points with the US commemorative coin program:
- The coins were designed/modeled by
Laura Gardin Fraser - an American artist/sculptress who designed multiple classic-era US commemorative coins.
- The coins were struck at the San Francisco Mint.
- The Philippines were a US Territory (and later, a US Commonwealth) between 1898 and 1946.
- General MacArthur will forever be linked to the freeing of the Philippines from Japanese occupation in World War II.
The low relief of the coins was the result of a production decision at the San Francisco Mint as it dealt with the post-war production requirements of
US coinage.

For more on the MacArthur coins, see:
1947 Philippines Macarthur Commemorative Coins - Origin Story