Went to Clearwater, FL two years ago with my Teknetics Eurotek. It seemed most of the town beaches had been recently reworked, cleaned, sifted, rebuilt. I didnt find squat except for some recently dropped coins, sunglasses, etc. There was one untamed little beach in a tiny town park where I found like 8 coins, but again...they were all no more than 20 or 30 years old, and more like only 10. Personally, I would eventually like to find a PI detector for beach use. I dont care if I have to dig alot of sand. FYI, I just scored a new Simplex today. I think that and a modestly priced PI would make a great beach couple!
I think beaches have been hunted so much by people with with high-end VLF, you're going to need PI to find what they missed, at least if you're looking for old stuff. I think in many obvious hunting grounds the good stuff is going to be down deep. Occasionally quirky weather and time itself churns up new finds from the depths, or buries new stuff...but mostly the old stuff will be deep...and one doesnt need an $800 detector to find rings that were just lost a few months ago. Any decent gold ring within 5" is going be a solid hit, IMO, with most detectors intermediate and above. As long as you're using a 14khz or above machine, anyway. A 19khz single freq machine is a good choice if you dont have a Nox, IMO again.
But anyway I echo what Huckleberry was saying: Beaches are usually truly in a state of constant flux, and commercial beaches have the added parameter of being cleaned and re-sanded. They have guys periodically dragging screens behind tractors and ATVs in those places! Sometimes I wonder what those guys bring home without even needing a detector! I havent seen ANYTHING written about that online. Must be a guarded secret. I wonder if there are things about that process and the people involved that would be useful to know.
It would be interesting to drop a tiny pinging transmitter on a beach in the tidal zone, that would be similar to a large coin in size and weight...and monitor its movement over an entire month. I'd be curious if the tendency would be more to get buried, migrate wildly around between surf and turf...or be pulled further and further out to sea.