As of about 15 years ago, Rudford's diner in San Diego (El Cajon Blvd) had pay toilets with the real authentic coin boxes on them. You didn't actually need to pay your own money; any waitress could provide you a coin when you asked. IIRC, they may have run on tokens only, so that it would be a closed ecosystem.

That may have been the only place I ever saw the real pay-toilet coin boxes. Anywhere else was simply gatekept by being a patron of the restaurant or store. Of course, in 1980s San Diego, there were zero public toilets of any kind, anywhere in town. All of the toilets were inside businesses, maintained by those businesses, and 100% closed to non-customers.