There is no 57b source/compile. All the binaries are named 9.xxb internally, where 9 represents 9999, xx is last 2 numbers of the released source (9999 57 ), and b is simply beta. Just like previous releases were 9.58b, 9.63b, 9.64b, 9.65b, 9.66b, 9.67b, 9.68b, 9.70b, 9.73b, 9.76b, 9.81b, 9.84b, 9 ...