[Enesuygurs]

With ignore_case=True, country_code() and currency() compare value.upper() against the ISO 3166 / ISO 4217 lists. str.upper() maps some non-ASCII letters onto ASCII ones, so values that are not ISO codes are accepted:

• currency("uſd", ignore_case=True) returns True (long s, becomes USD)
• currency("ıls", ignore_case=True) returns True (dotless i, becomes ILS)
• country_code("ıt", ignore_case=True) returns True (becomes IT)
• country_code("ıta", ignore_case=True) returns True (becomes ITA)
• country_code("fiN", iso_format="alpha3", ignore_case=True) returns True (the 2-character value becomes FIN)

This is the same class of issue that was fixed for IBANs in #512. The fix requires ASCII input before the case-insensitive lookup. ASCII codes in any case, and the currency symbol check (skip_symbols=False), behave as before.

The new parametrized test cases fail before this change and pass after it. The full suite passes (1522 tests, plus 58 doctests), and ruff check, ruff format --check and pyright are clean on the changed files.

[agammann]

I reviewed the country and currency lookup guards at f63135a. They reject Unicode letters that uppercase into ASCII ISO codes while keeping ASCII mixed-case inputs valid; the existing currency-symbol branch still runs before the ASCII guard. The country/currency test module passes locally (37 tests on Python 3.14.8). I did not run the full suite or platform matrix.