Much to the chagrin of many in the investment community, Apple (AAPL 1.67%) does not break out its unit sales and revenues of its newest product category, the Apple Watch. This "secrecy" is, according to Apple CEO Tim Cook, due to Apple not wanting to give its competition "insight."

Investors can, with some guesswork and sensible assumptions around average selling price, get a reasonable handle on how this business is doing by looking at the changes in revenue in the company's "Other Products" segment.

Interestingly, though, at a recent meeting with Apple employees, Apple executives reportedly revealed some very interesting unit shipment numbers for Apple Watch during the first quarter of the company's fiscal 2016.

Better holiday sales than the original iPhone
9to5Mac, citing "multiple sources" in attendance of this event, reports that Cook said that Apple Watch sales last quarter exceeded sales of the original iPhone during its very first holiday quarter all the way back in 2007.

According to Apple's form 10-K filing from February 1, 2008, Apple sold 2.315 million iPhones in the quarter ending on Dec. 29, 2007.

Given that blended average selling prices of Apple Watch are likely lower than those of the original iPhone, whether Cook was referring to revenue or units, we know that Apple sold at least 2.315 million Apple Watch units during the most recent quarter.

So far so good, but will the momentum continue?
Given how popular Apple is, and given that the Apple Watch represents Apple's "next big thing," it's not surprising to see it do so well during its first year (though it probably isn't living up to the hyper-inflated expectations from a number of the sell-side analysts).

The key thing to watch will be whether Apple Watch will continue to see momentum in the coming quarters/years.

On one hand, I'm inclined to be optimistic because there's just so much that the current Apple Watch can't do that it will be able to do as technology advances. The current model has very weak hardware inside, which fundamentally limits it as a computing device. I suspect that as technology advances (particularly ultra-low power chip manufacturing technology), the Apple Watch will be unleashed in much the same way that the iPhone was.

On the other hand, I can't help but wonder if the Apple Watch will see the same fate as the iPad. This product category was white-hot for a while, with industry and stock market analysts predicting that tablets in general would simply continue to grow and grow.

The reality is that tablet upgrade cycles are long and they were, to a very real extent, cannibalized by the proliferation of larger-screen smartphones.

I believe that Apple Watch upgrade cycles will be at least as long as iPad upgrade cycles, if not even longer. This means that Apple should enjoy revenue growth as the products go increasingly mainstream, but once most of the folks who want Apple Watches have them, sales may nose-dive much in the same way that iPad sales have over the last year or so.

It'll be interesting to see how this all plays out over the next couple of years, that's for sure!