I'd never heard of a Caballero, until I saw this at the Coronado annual car show, Orange and Isabella

Best of Show winner at the annual GoodGuys show.
Because the Century was considered the senior "small Buick", the model received GM's only hardtop station wagon, the Century Caballero, from 1957 through 1958. The Caballero's expensive tooling, plus its limited sales appeal, caused GM to abandon the hardtop station wagon body style going into its planned 1959 divisional-wide new design program.
http://en.wikipedia.org/wiki/Buick_Century
The most remarkable part of this wagon is the wrap around rear window that raised up. Sorry i didn't take a picture of it now.