Apple User Agents do not expose the hardware version, so you can only guess the iPhone version by the OS version, for example, if it's running iOS 5, it must be an iPhone 4 or 4S. In fact, it's even very hard (perhaps impossible) to distinguish between iPhone 4 and 4S from native apps.
Anyway, the other answer is incorrect, that UA must be from an iPhone 3, 3GS or a really outdated iPhone 4, but it cannot be from a 4S because the 4S shipped with iOS 5. Here's a selection of iPhone 4/4S UAs I've seen today:
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Mobile/9A405
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Mobile/9A406
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Ver sion/5.1 Mobile/9A405 Safari/7534.48.3
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A405 Safari/7534.48.3
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A406 Safari/7534.48.3
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Mobile/9A334
Mozilla/5.0 (iPhone; CPU iPhone OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A334 Safari/7534.48.3
Mozilla/5.0 (iPhone; CPU iPhone OS 5_1 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9B179 Safari/7534.48.3
With regards to WURFL, I am the COO of ScientiaMobile (WURFL owner), and I can say that no public access to our data has been removed since our formation. You are welcome to browse our devices and user agents at the ScientiaMobile WURFL Explorer.