Here in CA, there are CCC camp locations on what is now Fed, and state land both. When they fall under current fed. land (like on a military base, or fed park, etc..), I have been told by a passing ranger that I would need to turn in any coins older than 50 yrs. old He drove off and never even said where I was to turn them in to. Nor did/does anyone ever check. In other words, it appeared to be an honor system, and left up to the skills of your math
At CCC camps that were located on what is now state property, of course, that would vary from state to state. Personally, in CA (just to use that as an example), I'm sure if a person were to look deep enough and hard enough, he'd find depressing wording for state land. But there are state parks & beaches around me, that are detected all the time, in plain view, & no one is ever bothered. Of course, if you were to go to a bureaucrat's desk in the state capitol, with a shovel in your hand, and ask "can I metal detect there?" you would probably get a "no". But apparently the rank and file at some state parks just aren't aware of that minutia, or simply have better things to do. Maybe it's better left that way

Ie.: as long as we're not in obvious historical monuments, or being a nuisance, (or not ignoring a warning) we're not bothered. And in those cases, if you asked, and they looked it up and told you "no", guess what's gonig to happen the next time they see
another guy detecting, that they would previously have probably never paid attention to? They'll remember the earlier inquiry and think "aha, there's one of
them!" (I've actually seen that psychology played out several times)