Quoted from fuseholder:1933 Bally Blue Ribbon.
I just picked up a 1965 Bally "Blue Ribbon". According to IPDB only 875 made. Some of those are German versions. Mine is American, and it's the only one I've ever seen!
But, I also own a Gottlieb "Pleasure Isle". Only 235 of them made, but oddly, I've seen several of these in person, and many others for sale on eBay, etc.
Also have several low production add-a-ball wedgeheads. Many had a production run of less than 650 units, such as "Dimension" (490), and "Mini Pool" (500).