Microsoft has hit the release to manufacturing (RTM) milestone with Windows 10 for PCs, according to sources.

The build designated as RTM is 10240, sources say. (The Verge is hearing the same, I see.)

I've asked Microsoft whether it will confirm officially that Windows 10 for PCs has hit RTM. No word back so far.

Update: Microsoft just released Build 10240 to its Fast and Slow Ring Insiders on July 15. The post from Windows Insider chief Gabe Aul doesn't call out this build as RTM or an RTM candidate. But he also doesn't say it isn't. The build is designated as "TH1" according to Insiders. My bet is that stands for "Threshold 1." (Threshold was the codename for Windows 10.)

Update 2: Is this considered RTM? The official response from a Microsoft spokesperson:

"This build is the latest Windows 10 build, and we'll continue to update Windows 10 code as we head toward launch and beyond. We are embracing a new way to deliver Windows."

Microsoft released to its Windows Insiders on the Fast Ring Windows 10 preview Build 10166 last week. Earlier this week, Microsoft officials told Insiders that the company was suspending temporarily availability of Windows 10 preview builds in preparation for RTM.

Microsoft's next step is to make its RTM code available to its hardware and retail partners.

The company will begin making Windows 10 RTM code available on July 29, starting with its Windows Insider testers. After that date, Microsoft will make Windows 10 RTM available to other users who have reserved their free copies of the Windows 10 update.The Windows 10 update will be available to consumers who are running Genuine copies of Windows 7, Windows 8 and Windows 8.1. The update will be free for a year -- from July 29, 2015 to July 29, 2016.

After that point, Microsoft is expected to charge customers running Windows 7/8 some amount of money to upgrade to Windows 10. The Windows 10 free upgrade deal is not available to Enterprise users.

Microsoft will continue to deliver regular feature updates and security fixes to those who upgrade for free via Windows Update. In fact, I wouldn't be surprised to see Microsoft release some updates for Windows 10 that the company has built between now and July 29 to those who get the OS starting July 29.

I've heard that Microsoft officials have no plans to formally announce RTM, since the RTM designation has a lot less meaning in a world where Windows is a continuously updated service.

An interesting coincidence: Yesterday, July 14, was the day that Windows 95 hit RTM, 20 years ago.

As Microsoft Chief Operating Officer Kevin Turner noted during his July 15 Worldwide Partner Conference keynote, Windows 10 is the "last monolithic release we had built around a three-year upgrade cycle." Windows 10 is Windows as a service, Turner added.