"Generator Breaker" without further explanation opens things up to all sorts of interpretations. At one end of the scale, Bill has your answer. But that's a far cry from a 24kV generator breaker that has a 20kA thermal rating; no not an interrupting rating of 20kA, but a continuous current rating of 20kA. Also a rather specialized device but vastly different. For some ranges of voltage and current some "normal" breakers are suitable for generator applications. It depends.
I’ll see your silver lining and raise you two black clouds. - Protection Operations