If you hunt dry sand, you will almost always only find modern clad. That's not a bad thing, mind you, because any time you get enough "targets" on the beach (whether dry or wet sand), there's the chance at jewelry, which .... of course.... beaches make "condusive" conditions for jewelry losses.
If you hunt the wet sand (like looking for the tell-tale formations where hopefully mother nature groups heavier targets), you will .... again .... mostly get modern targets. HOWEVER, the old coins you've heard of being found on the beach, are usually almost always persons who get on to certain beaches, after high swells, on-shore winds, and high tides coincide to produce severe beach erosion. If it goes down into zones/stratas where older coins are, then presto, you get older coins.
But there's a lot of other factors though: Some beaches don't fluctuate too much annually (like protected inner-harbor beaches, or beaches against cliffs where it erodes annually down to bedrock over and over, etc... Obviously flukes occur, and sometimes a silver coin is found amidst a pattern of recent losses out on the wet. This occurs because targets come back in during the spring/summer buildup of sand, where sand comes back on-shore to rebuild the beaches, during the natural "in and out" action of the sand. But those are usually just random, with no rhyme or reason.
The best opportunity for old coins, is when the over-night erosion has occured all-at-once, turning the beach into a giant riffle-board/sluice-box action. Ideally perhaps cutting back into dry dunes that haven't seen waves reach that high in decades. Or down to bed-rock layer beyond which no targets can sink any further than (so the old coins are stuck in a moon-scape bedrock layer).
But if your particular beach was hit at some time in the past decades by a SUPER storm that ALREADY scoured down to insane depths and pulled the targets WAY out (like major hurricanes back in the 1960s, etc...), then there are some beaches where .... it seems that no one has ever found an old coin ever again. I've seen this phenomenom here on the west coast, where some storms in the winter of 1982-83 were SO SEVERE (and we got SO much silver off them during that time), that we saw perpendicular cuts 10 to 15 ft. high on some beaches! Naturally no one got "all the silver coins" back then, but what
DID happen, it seems, is that when the sand finally came back in on a few that following summer, that apparently the older coins stayed out in the ocean. Who knows? Because I know of one beach where ........ to this day ........ no one's ever found an old coin again (barring a few flukes), even in big storms since then.
So some would say that you need a storm that exceeds all previous ones, to get down *further* than those previous ones. However, you can't say that uniformly. Because certain storms, although fierce, will affect beaches only at certain points. You know, like "burrs in mother nature's bonnet", were certain spots get giant scallops and cuts, while a mere 1/2 mile south of north of there, was less affected. Or one storm erodes "down", while the next goes further "back", and so forth.
Anyhow, sorry for the long answer, but the short answer is: storm erosion increases your chances at oldies
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