Agree
I’ve seen a few lead bars, relatively young, gray and oxidized.
Tin in the alloy will help, though.
If I understand the theory right, silver in the bars would supposedly act like tin, but even that will oxidize quickly in terms of being underground for 2,000 years. Found in farmland too; I’ve pulled up a lot of minie balls and round ball from farmland, ain’t never came across an example that’d hold such a pattern.
Lead hardened with Linotype also oxidizes over time.