One of the most consistent iPhone rumors we’ve been hearing over the past few years has been that the Cupertino company is working on a ‘nano’ version of its popular smartphone.

Obviously, nothing has ever materialized, but for some reason the iPhone Nano always seems to surface in the rumor run-up right before Apple releases a new handset. But why? The folks over at PatentlyApple might have the answer…

According to the site, the US Patent and Trademark Office granted the iPhone-makers a series of 20 patents today ranging from multi-touch to iPad docks. But perhaps the most interesting of the bunch is a patent regarding an early iPhone Nano concept.

Here’s PatentlyApple’s thoughts on the filing:

“That last patent isn’t about a specific phone design in the least and yet it may illustrate that an iPhone-nano like design was very much on the minds of Apple’s engineers back in 2006. Is that idea now scrapped being that iPhone subsidies allow older models of full size iPhones to sell for only $99 — or is it a concept that’s still on Apple’s roadmap? Time will tell.”

Actually the 3GS is $0 at AT&T. And with three models of the iPhone currently hitting all of the major price points in the market, I don’t see where an iPhone Nano fits in. But the fact that one existed inside the company’s R&D labs at one point is still intriguing.

Was it a smart move on Apple’s part not to release the device?

[9to5Mac]