there is no "holes". It's a set of rotating "tongs". The tongs are like on a conveyer, and drop the debri into a hopper. And it's like the others here are telling you: It *might* catch a necklace, and best. I suppose a one-in-a-million shot and a tong catching a ring? They are basically made to pick up McDonalds bags, wood debri from bonfire residue, bottles and cans, etc... Not small stuff.
There was one type of beach sifter made that has an agitating system to sift the sand through holes. And apparently the size of the holes was adjustable by the operator. But to set it so small as to catch coin-sized items (down to cigarette butts), was a real chore for the machine to do. It caused great drag on the components, starts to take forever to cover ground, etc... So not only was that particular type of beach cleaner not sold very much , but maybe that type is not even made anymore? Most all beach cleaners are of the tong/rake style type.