This time it’s the 2nd release of Windows 7 Milestone 1. Version 6.1 (build 6574.1.{SECRET}). The {SECRET} here means I won’t expose detail.

No, even Milestone 1 isn’t a single release. Microsoft releases multiple versions of M1 with different minor version numbers. Well, for me it is the 2nd one I’ve gotten but I’ve no idea about how many releases Microsoft did before. I’ll use Win7 M1 R2, which stands for Windows 7 Milestone 1 Release 2, to describe it in the following. Please be noted, ‘Release 2’ is my naming convention, not Microsoft’s.

Source: ThinkNext