Mr- wilburino is right : abundance of clad doesn't mean it hasn't been hit . Hardcore hunters of yesteryear and today will oftentime pass shallow clad and go only for the deepies . And then add a decade of recent clad drops, & you could have a hard-hit area ..... yet with lots of clad . I can think of parks where Icould rack up 100 easy clad, yet slim chances of finding silver there nowadays.
I think it dates back to the early 60's. it was used until recently, still a fence around it, I got access through my job. We did find one good piece of jewelry and hunted about 1/50th of the area. Tons of clad from 60-70's in a few hours. No silver coins yet, but I don't know how someone could have picked out all the silver and bypassed all the clad. Alot of the silver rings up in same zone as clad.