Does anyone know a way to detect the older set of devices:
From the newer
Have you looked into the UserAgent string?
For example, my iPhone 4 returns:
Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0_1 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A306 Safari/6531.22.7
The Mobile/8A306
is the firmware version (just google for 8a306 iphone
I believe the older versions of the phones cannot run the new versions of the OS. So you might be able to find a set of firmware codes that will only show up on the older versions of the phones. This will at least allow you to detect some of the differences.
The WURFL has some good references and user agent strings and how to detect the device and capabilities based on it. There is a browseable list of them, and they might be able to detect the devices correctly. I don't have access to the older hardware, so I can't confirm it works all the time. You can explore what your device shows up as using: http://www.tera-wurfl.com/explore/ And to look at the various UserAgent strings given back.