metal-addict : Have you ever done Fuller Park in Napa ? I've pulled a few old silver, and some random wheaties there. Even a teens walker half, as I recall.
It's been hit HARD ! But the newer generations of Minelabs (explorer, in my case) seem to punch a tad deeper than the yesteryear guys in that area who were primarily swinging Whites.
It's not for the "faint-of-heart" (if you're not well-versed in turf-strategy). But just sayin' that there's still some deep elusive silver in there, for those that can eek it out.