The Polhemus stamp on foreign coins is noteworthy as it demonstrates that as late as 1857, foreign coins still constituted a substantial portion, if not a majority, of the United States circulating coinage, at least in California.
Coincidentally (?) 1857 (Feb 21) is the year that the United States Congress withdrew the legal tender status of foreign coins.
James Lozier Polhemus (1825 - 1866) arrived in California in 1849. (1). The store at “190 J Street” began operations in about 1853. (2). The business was continued by Mrs. Polhemus until 1874.
James Polhemus reportedly stamped all the coins that passed through his till. (1). The last known dated piece that he stamped is an 1857 double eagle that was recovered from the wreck of the SS Central America.
(1) Brunk - Merchant & Privately Countermarked Coins
(2) Rulau - Standard Catalog of U.S. Tokens
As coin bearing a Polhemus stamp circulated in California in the Gold Rush era, the 70 + known examples give us an idea of the that period's circulating coinage:
(7) 10 cents: U.S. dimes 1837 to 1856
(3) 1 Real (Spanish American 1776; Chile 1844,Mexico 1849)
(1) Austrian Italy Milan 1 Lire
(1) 50 Centimes (France) 1850
(1) 20 Centavos Chile
(30) 25 cents: U.S. Quarters 1838 - 1856
(7) Spanish American 2 Reales 1782-1849)
(4) Great Britain Shilling 1816-1828
(1) British East India Company Rupee
(12) 50 cents: U.S. Half Dollar 1843 - 1856
(1) Bolivia 4 Soles
(1) $1.00 Dollar U.S. Dollar (1843)
(6) Foreign Crowns
Chile 1 peso
England (1) 1844
Franc 5 Francs (2)
Nueva Grenada 8R (1838)
Russia Rouble (1855)
(3) $20.00: U.S. Double Eagles 1855-1857
No Polhemus stamps are known on copper coins.
This 1830 5 Francs with the Polhemus stamp is possibly the earliest dated "silver dollar" sized coin that can be demonstrated to have circulated in California.