When I replaced a service a few months ago, I got enough Cu to make the run from the meter box to the panel, just in case.
When I opened everything up, the old entrance (60A) was Al, when they upgraded a few years ago, they re-used it, and ran Cu for the other leg. I stripped out the Al (It was too short for the new panel...darn
) and replaced it with new THHN/THWN Cu.
I don't completely trust Al...