Jerome, on Dan 2:39

“And after thee shall rise up another kingdom, inferior to thee, of silver: and another third kingdom of brass, which shall rule over all the world.”

“Verse 39. "And after thee there shall arise another empire inferior to thee, made of silver." (The Vulgate LXX does not include "made of silver.") That is to say, the empire of the Medes and Persians, which bears a resemblance to silver, being inferior to the preceding empire, and superior to that which is to follow. "And a third empire of bronze (the Vulgate LXX has "made of copper"), which shall rule over the entire earth." This signifies the Alexandrian empire, and that of the Macedonians, and of Alexander's successors. Now this is properly termed brazen, for among all the metals bronze possesses an outstanding resonance and a clear ring, and the blast of a brazen trumpet is heard far and wide, so that it signifies not only the fame and power of the empire but also the eloquence of the Greek language.”

Imported from an open dataset — not yet checked against the printed edition.