In a filing with the US Security and Exchange Commission (SEC), Microsoft admitted something it has been silent about with the public: Yes, the first Surface tablets will ship to customers on October 26, the same day that Windows 8 arrives.

"The next version of our operating system, Windows 8, will be generally available on October 26, 2012,” the filing reads. “At that time, we will begin selling the Surface, a series of Microsoft-designed and manufactured hardware devices.”

Presumably, this means only the base Surface version, which runs on ARM hardware and utilizes the ARM version of Windows 8, called Windows RT. Surface Pro, which runs Windows 8 Pro on Intel-based hardware, will arrive about 90 days later, according to a previous Microsoft statement.

Of course, there are still so many questions about Surface, not the least of which is pricing. The ARM-based Surface versions will come in 32GB and 64GB variants, and the Intel Pro versions will ship with 64GB or 128GB of solid state storage. But Microsoft has never discussed pricing, and even the SEC filing doesn’t touch on this matter.

"Suggested retail pricing will be announced closer to availability and is expected to be competitive with a comparable ARM tablet or Intel Ultrabook-class PC," Microsoft said in a statement, somewhat clarifying things. Comparable ARM tablets, like the iPad, start at $500 and quickly rise to $830. Ultrabooks generally sell in the $999 range, though Intel said recently that it expects Windows 8-class Ultrabooks to sell for closer to $699.

Anyway, the Surface mentions in Microsoft’s annual CES filing previously received some press attention because the company admits that its entry into the hardware market could harm its relationship with PC makers. (Not that you have to be a psychiatrist to have figured out that one in advance.) Closet analysts have long played up these filings as a peek into Microsoft’s inner soul, but that’s actually truer than it’s ever been given the company’s recent descent into revelation paranoia.

Why the secrecy? We’ll never know for sure about Microsoft’s motivations, but as CEO Steve Ballmer noted at the firm’s Worldwide Partner Conference earlier this month, Microsoft is pleased with its recent forays into Apple-type secrecy. Its Surface launch event, essentially a silly promotional secret that was only revealed at the last second, is considered a huge success inside the company, for example. We’re going to be dealing with this lack of transparency for years to come, I think.