Mounting evidence hints that a new version of the iPhone has been in the works for some time now. This evidence emerged this week that suggests Apple Inc. has been testing its next generation iPhone in the San Francisco Bay Area for the last few months.

The development adds weight to rumors that the Cupertino, Calif. computer maker is preparing a smaller, lower cost version of its iconic smartphone for consumers grappling with the long, drawn out recession.

An Apple spokesman didn’t immediately respond to a request for comment.

The recent hubbub is over the discovery of the term “iPhone 2,1″ inside new iPhone software, and in data collected by Pinch Media Inc., an ad serving company used by iPhone software developers.

The numbers hold the clues. The first iPhone was identified in iPhone software as “iPhone 1,1″, while the next generation iPhone 3G went by the name “iPhone 1, 2.” If it sticks to this nomenclature, then “iPhone 2,1″ is the logical name for the brand new iPhone Apple’s rumored to be making now, said Pinch Media Chief Executive Greg Yardley.

The Apple news Web site MacRumors was the first to discover Apple’s new iPhone software describes an “iPhone 2,1″ model. In an interview Thursday, Pinch Media’s Yardley said data his company’s collected suggests Apple’s been running a small test of about 50 of these new iPhones in and around San Francisco since October.

“I don’t know what’s going on at Apple,” Yardley said. “But what we’re seeing though strongly indicates Apple’s doing some sort of new hardware testing.”