This "send it to us" type verbiage reminds me of the following:
When T'net was young (mid 1990s), there was only a single page, if I recall. So you had to scroll down the list of titles, to see if anything interested you to read. One thread title was to the effect of "California state beach legal ?". So.... being from CA, I opened that thread. Some dude was coming to so. CA on a business trip, and would be staying in a hotel "... next to such & such state beach". So he was wondering "is it legal/allowed?". As I read his question, my eyes focussed on the part about it being a "...state.." beach (as opposed to city, county, federal, etc...). And I thought about it for a moment, and realized that probably 90% of our coastline here in CA is administered by the state. That has the parking lots, restrooms, picnic tables, etc....
And I mentally pictured all the beaches in my part of CA, and knew they were all "state" beaches that we hunt . So I got ready to type out the answer to the guy that state beaches here are fair game. But before I typed out the "yes" answer, I saw that someone else had already answered his post. So I clicked on their answer first.
What I read was a real eye-opener to this "don't ask silly questions" attitude I now have: The other reply came from a person who made it simple. They merely gave the answer straight from the book called "Treasure Laws of the United States", by R. W. Doc Grim. That book was a sort of fore-runner to what the FMDAC now has on their website, of the state-by-state list. The author merely sent a xeroxed letter to all 50 states park's dept. headquarters. The letter asked "what are your laws regarding the use of metal detectors in your state's parks?" And perhaps detailed how the answers were to be compiled in a book he was writing. When the author got all 50 replies back, he merely puts them all in alphabetic state order, for this book. Even to the extent of being on state letterhead , so if any busy-bodies question you, you can show them straight from the horse's mouth.
A genius idea, right ? Then a person travelling state to state in RVs, can have this handy reference book to remove all doubt (avoid off-limits places, and have a ball where it's ok to do).
And the person posting this page of CA's reply, was figuring it applied to the OP's question. Since, of course, it's the very same park's dept that administers their beaches, as administers the inland parks. That is: There's no reasons why the rules of each wouldn't be the same.
And the answer shocked me, because it was very ... uh ... "dire" sounding. Like if you find an old coin (50 yr. or more?) you were to flag the spot with a little marker flag, and go alert the state archaeologist. Huh ?? This was news to me !! We'd been hunting state of CA beaches for 30 yrs. by then, and (gasp) yes we find old coins (like after storm erosion). And I had never heard of ANYONE hearing so much as "boo" for this. Oh sure, you might get flack if you were at one of the inland historically themed sensitive monument parks, but .... the beach for pete's sake ?
The reason I bring this all up is: How does one know, if and when they dutifully research the laws of where they're going, that the same psychology isn't at play ? I don't doubt you found that answer (that you must send in your old coin). But might it be no different than the situation I spell out here ? Mind you, if anyone here goes to state capitol in Sacramento and asks "does this apply to the beach?" and "does anyone *really* care?".... well of COURSE he will shriek as if you'd just asked to sleep with his wife. But as you can see, the reality is quite different. And if that same archie who just shrieked started getting requests to travel hither and yonder investigating little golf-T flags, or having envelopes arrive on his desk with 1950's wheaties, well .... guess what he'll recommend at the next annual meeting to devise new laws/rules ?
He said he asked the man at the table : "Where did you get these?" The man answered that "when it rains hard, they can be found in a certain gully wash off over at such & such (pointing to a direction in the hills). There is SO much history there, that I bet this story isn't inconceivable. 
