there are different types of beach-cleaner machines. The kind that just rake with tong-bars only get the big stuff. Eg.: McDonalds bags, soda bottles, etc... They can not pick up coin and ring sized stuff . Fortunately most of the beach cleaner machines are of this variety. Thus not a threat to us.
But then there's a more expensive type/brands that sifts the sand. And from what I've heard, there are adjustable settings where it can be made fine-tuned enough to pick up items as small as coins. Versus the wider settings that only pick up big stuff (and everything else falls back through).
The trouble with setting it to get smaller items, is that it's a big drag on the machine. It slows way down, uses more gas or diesel to cover the same square footage areas. Since the machine is having to work so much harder.
There's also a problem with setting the machine to get such-small targets, because then it will start to pick up twigs, seashells, pebbles, etc..... All of which are not trash, and just end up creating tons more disposal cost. So from what I hear, the operators don't use that fine tune setting (unless they simply want to have goodies to sort through at the end of the day, eh ? haha)
Also, the machines don't get close to fixed objects (eg.: volley-ball poles, lifeguard towers, etc....). And they don't do the wet inter-tidal zone. They only do the dry. And don't necessarily cover all the beach on any given day. And I think they only go a few inches (6" max?) deep.
So all in all, I don't think they're much of a threat to us.