Cudamark, I always enjoy your posts. You're right: There are various brands and model-types of beach cleaner machines. Most all of the are just rake conveyor types, that only get up McDonalds bags, bottles, cans, discarded towels, etc... But won't get coins and rings . At BEST a tong might catch a necklace chain.
But there is a certain type made, that has an agitating hopper box (like a trommel ?) where I've heard that the hole sizes are adjustable. And if the operator elects to make the hole sizes set to be smallest screen openings, it is indeed small enough to catch coins and rings. HOWEVER, it make the machine have to go very slow, and uses a lot more horsepower, fuel consumption, and coverage time to do. Because the machine is having to process much more material and force it through the holes.
That latter machine is, fortunately, used by very few of those places that have machines. And even then, very few that would set it on the time/energy consuming setting of the smallest hole/opening sizes. But I've heard of a city in So. CA, who has that. And their drivers relish the job, and PURPOSEFULLY set it the most refined setting . Even if it means volunteer over-time to finish their shift. Fortunately, that's just one city and just one stretch. That was long ago I heard that from a So. CA hunter, so not even sure if it's current info. .
But the machines don't do wet sand. And they don't get close to fixed objects like poles, walls, etc... And they only go a few inches deep at best. Hence even at a place where they employ the latter machine, they won't get it all. And it would only affect current dry sand losses, and have no bearing on beach storm erosion wet sand hunting.
