I knew lots of those guys, and have seen their collections. For the most part the modern era of metal detecting is a dessicated shadow of what it once was. I see so many people posting a lonely silver dime and saying "it's not hunted out!", but it IS hunted out when you consider that a person has to dig junk all day long to get that lonely silver dime.
It's a hobby of diminishing returns, and there is no getting around it. I still have lots of fun and make good finds, but I abandoned the City Park years ago.
There are different frontiers now. But the day and age of pulling silver from turfed parks, has become very difficult in some regions. In my region, for instance, the beginner is simply not going to go to turfed parks and expect to get silver. They're going to have a tough time indeed. Not sure about other parts of the USA.
I remember when .... in the main park in the middle of our city , you could take a beginner there to train them. And on their first day, they could usually expect to at least get wheaties, if not a silver dime. And a proficient user would routinely pull 4 to 8 silver @ at a pop. That was the very late 1970s into the early 1980s. But pity the poor fellow today who tries to go there now and pull silver. Not only were all the easy-4-star classic deepie signals cherry-picked, but you now have:
a) 30 to 35 yrs. of clad added.
b) 30 to 35 yrs. of foil and tabs added
c) the silver is simply all the more deeper (go figure, in 1981 to 82-ish, silver had only been out of circulation for 20-odd years)
Nowadays, even the most hardcore turf-hunters would be doing good to eek out an added silver dime from the sea of zinc and foil. If a guy just darted around and cherry picked for clad, sure, he'd tally up $5.00 no problem. Or if he wanted to angle for gold, sure, he could dig 300 low conductors and eventually net a ring.