Depending on which of today’s Best Buy-related iPhone 5 reports you want to give the most credence to, the highly anticipated gadget could launch during the first week of October, or a bit later, on October 21st.

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Boy Genius Report’s Jonathan Geller says a tipster handed the blog a leaked Best Buy document labeled “Promotional activity” and carrying a subheading of “Week 9/4.”

The document, real or otherwise, says, “iPhone 5 product introduction expected, pre-sales begin for expected week 1 launch / Sprint launches iPhone 5.” It also says “(Apple product information/Launch dates subject to change).”

On the other hand, This Is My Next’s Chris Ziegler reports that TIMN received a tip about a mysterious “Apple fixture” that’s scheduled to be installed at an unnamed Best Buy location October 21. The site displays a screenshot that shows what may or may not be an authentic online Best Buy “National Retail Calendar.”

“Process Display or Granger will be installing an Apple fixture on the large C2 end displays. Please ensure a manager/key carrier is available at 6:00 am for access to the store,” the retail calendar says, in a rather cloak-and-dagger fashion. This Is My Next says its tipster called the 6 am show-up time unusual–managers usually don’t have to arrive till an hour later. The tipster also reported an October 10 meeting to “discuss BIG release dates.”

As Ziegler points out, The Wall Street Journal has reported that Sprint Nextel will begin selling the iPhone 5 in mid-October. Other reports, though, have set the date as earlier in the month.

And, of course, my colleagues Declan McCullagh and Greg Sandoval recently broke the news that another unreleased iPhone prototype had apparently recharged itself a little two energetically while at a bar and had gone missing. (You’ll recall, I’m sure, that it’s not the first time such a thing has happened.) McCullagh and Sandoval also note that the file name of a San Francisco Police Department document seems to peg the prototype as the iPhone 5 and that Apple is taking unusual steps to get the gadget back.