I'm not what you want to know...
Generally, Cavalier, Vendo & Westinghouse added these water fountains, "bubblers" according to some literature, to machines/coolers with the idea that a thirsty person might stop for a drink and then purchase a soda...
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In your case, it's probably a stainless steel fountain but there where porcelain fountains in earlier years.
A water supply was attached to one of the inlets, the other would go to the fountain itself. The water would sit in the coils and get cold from the refrigerated compartment. The cold water would only last as long as the amount of water the coils could hold at any given time...