I tried here
Hey guys, did you see how old this post is? I was one of the ones who chimed in back when the fellow first posed his question, as you can see. As it turns out, the fellow and I discussed the matter further through PM's, and he spelled out a little bit more of the situation, the actual location, etc.... It was/is only a few hours from where I live in CA. So I told him that the next time I was passing through his area, I would give it a try with various methods, and let him know what the results were (so that .... presumably .... he would join in with me, if it were any good).
A month or two later, I found myself in his part of the state on other un-related business, so I swung by to take a look. The metal bleachers sit only 6 or 8" above the ground. So using any kind of standard coil is out of the question, as you'd merely be picking up the signals above the coil. And the trusses (upright supports) are also close enough spaced that .... even the unique Garrett coil that only sees down (but not up), might also be problemsome. After trying various things, it turned out that the Minelab in-line probe worked the best. But naturally, coverage was tedious, to cover ground very quickly. As his post said, you can practically eye-ball the coins (once your eyes adjust to the shadows of the underbelly of these seatings). So depth was not the issue. And nails were everywhere, screws, rivots, etc.... from the construction and upkeep of the metal seating over the years.
And no, southern digger, screening the entire contents of a stadium's under-belly is simply not an option (the coins in any one spot are not prolific enough to merit such extenses). You simply could not process that amount of dirt, to be worthwhile, for this particular site. I mean, as slow as a probe is, you'd still be faster doing that, than thinking you're going to screen dozens of acres!

And sure, a bunch nails over a coin will mask that coin *even* with a probe. So nothing is perfect.
My take was about 100 coins, of which I recall about 6 or 7 were silver, and a handful of wheaties. As was said, the bleachers only date to 1950, so nothing was particularly old. After getting these reconn. results, I tried emailing and PM'ing the fellow (who works at this college), and could not get ahold of him. I dunno whatever happened to him. He was not an md'r, and had just, I guess, found T'net through googling, upon being inspired after eye-balling coins down there.
The place is still worth a try, for anyone who's close, and wants to goof around for silver roosies and washingtons. And no, I didn't angle for jewelry, because it's a sea of tabs and foil under there. I high disc'd.