There are usually only one gold master or GM released to developers before the final macOS is released. This time, though, Apple outed a second GM for macOS Sierra a few days before official release. The new build is labeled 16A323. One GM is usually released because it’s supposed to represent finished code. However, there are cases like these when companies spot bugs that need to be fixed as soon as possible. Sierra will be a free updae for Mac owners and will be bringing Siri and Apple Pay to the brand’s desktop OS.
Source: Apple Insider