Yeah, I saw those. The 14YJ (which all that sold today were) is the PBR jet, but the ones that were for sale looked too new to be originals. They are still available new, from North American Marine Jet, so these were probably ones bought as replacements- and possibly meant to be SAP aid to countries still using the PBR (like the Philippines). North American Marine Jet bought out Jacuzzi in the mid 80s, which dates those jets as at least 80s or newer. But the 14YJ is a commercial jet, so they had plenty of other uses. The N300 (the successor to the 14YJ) is commonly used in Bristol Bay herring boats.
I'm partial to Hamilton jets myself... being that my boat has one.