I'm trying to ascertain why some foreign coins stuck at United States Mints during WWII bear a U.S. Mint mark. Published statements are consistently vague. Examples:

Charles G. Altz & E.H. Barton (Foreign Coins Stuck At United States Mints, Whitman Publishing, 1965, one of the "Black Books") wrote:

Tim Ziebarth (pdxcoinclub.org), Foreign Coins Manufactured at US Mints, March 2006, wrote:

Any insights or references would be appreciated.

The production of foreign coins by US Mints began in 1833 with the striking of a Liberia (LR) one cent coin. The Liberia one cent, in essence a token dated 1833, was struck by the Mint for theAmerican Colonization Society, founded in 1817 for the sole purpose of transporting "freeborn blacks" and "emancipated slaves" back to Africa.

The U.S. Mint had long been in the business of striking medals for various groups and artists. In fact, the U.S. Mint was the only place to go in North America if you wanted a large sized medalstruck, since no other equipment was available that could handle the immense pressures required to strike such pieces. The prospect of the mint manufacturing tokens, as in the case of the Liberiancents, was not a far offshoot from the medal making business. It is believed that the medal manufacturing activities of the mint led to some of the very first foreign coinage struck by the U.S.Mint.

The one-cent token featured "Freed Negro" standing next to a palm tree, with a ship in the distance. Though many regard the one-cent piece a "hard times" token, and thus not acknowledged by the USmint as foreign coinage in its annual reports, it did function as coinage in the Liberian colony

Official and wide-scale minting of Foreign coins began in the US with the passage of the Act of January 29, 1874 which read:

The first coins struck under this new authorization were 1 and 2 ½ centavo issues in 1875-76 for Venezuela in a Copper-Nickel-Zinc (mintage of 10 and 2 million respectively) at the PhiladelphiaMint, and were dated 1876 and 1877.

To read the complete article, see:
Foreign Coins Struck at U.S. Mints(http://pdxcoinclub.org/articles/Foreign%20Coins
%20Struck%20at%20US%20Mints%20CWNA%20article%20with%20table.pdf)

Eric von Klinger wrote:

To read the complete article, see: A VERY AMERICAN CENT! THE ACS LIBERIA CENT TOKENS OF 1833(https://www.archive.org/stream/PennyWiseVol40No5#page/n3/mode/2up)

To read the complete article, see:
Freed slaves in Sierra Leone order coins struck in Britain(https://www.coinworld.com/news/world-coins/2018/01/freed-slaves-in-sierra-leone-order-british-struck-coins.html)

To read the earlier E-Sylum articles, see:
DOMESTIC AND FOREIGN COINS MANUFACTURED BY MINTS OF THE U.S (http://www.coinbooks.org/esylum_v15n41a16.html)
MORE ON DOMESTIC AND FOREIGN COINS FROM U.S. MINTS (http://www.coinbooks.org/esylum_v15n42a08.html)