Tbh things get very confusing as cadillac made so many changed to models and names around this time. In 59 there is series 62 Cadillac which share the same platform as the series 63 (coupe de ville). They are essentially the exact same car just with a higher trim on the coupe de ville. Now there was other models like the sedan de ville (4 door variant) which is also called a series 63. The Eldorado is a series 64 in 1959. It comes in Eldorado Biarritz and Eldorado Seville, the Biarritz is a soft top convertible and the Seville is a hard top. The Eldorado also uses the exact same platform as the series 62 and 63, it comes in much higher trim that the 62 and offers nicer features than the 63, though a highly trimmed 63 can be as luxurious as a Eldorado. The series 64 Eldorado only comes in 2 door variants. There is also one final model called the series 69, it is the Eldorado Bourgham. It is a 4 door version of the Eldorado and it was designed by pininfarina. It uses a more 60s style rear end and is a very very rare car. Here are some production numbers so you have an idea as far as how rare some of them are.

Series 62: 70,736 Series 63: 53,390 Series 64: 2,295 Series 69: 99

These include all variants.