For example, he points out that old French Franc coins (1959-2001)
https://en.numista.com/catalogue/pieces6.html[wt: 6 g/dia.: 24 mm/thickness: 1.79mm];
Barbados 25 cents (1973- 2006)
https://en.numista.com/catalogue/pieces917.html[5.67 g/23 mm/1.82 mm]
and Dominican 25 centavos (1989-91)
https://en.numista.com/catalogue/pieces1089.html[5.7 g/24.25 mm/1.87]
-- all very closely match the US quarter :
[5.67 g/24.26 mm/1.75 mm] ......
The problem for the business people is that the French francs are basically worthless, the Barbadian (sp?) 'quarter' is worth about 13 US cents, and the Dominican "quarter" is worth about a half-cent.
He says over the last few years he's been flooded with these coins, plus old Belgian 5 franc coins, old Jamaican 10 cents coins, etc., all masquerading as US quarters!
It causes him headaches because his bank has to write up discrepancy reports and even return the foreign coins in some circumstances as 'proof' .... all costly extra-steps.
He went to a convention earlier this year and these coin 'masqueraders' and what the banking establishment could do about them was even the subject of two speakers.
He says at his facility, over $50,000 or so a week is 'caught', so it's not trifling amount.