The Chorus uses the metaphor of Athenians mistaking phony, silver-plated copper coins for real gold to suggest that Athenians no longer know how to identify (and elect to office) reputable people of noble character, and this is why they’re presently in a politically vulnerable situation (at the time of
The Frogs’s first performance, the Peloponnesian War was nearing its end—Athens was on the verge of collapse and would surrender to Sparta the following year).