Apple is about to sell its 10 millionth iPad, if it hasn't already -- barring a total collapse in sales.

Through Apple's September quarter, it had sold about 7.5 million iPads since launching the product in April. (And, if you recall, there were supply constraints that made last quarter's iPad sales -- 4.2 million -- a big disappointment.)

Piper Jaffray analyst Gene Munster expects Apple to ship 5.5 million iPads this quarter. (More than $3.5 billion in revenue!)

Even assuming that the vast majority of those sales are in mid-to-late December for the holidays, it's possible that Apple has now already sold its 10 millionth iPad.

If it hasn't, it should happen very soon.

That is a HUGE hit.

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