For your convenience, the Model Identifier (sometimes called Machine Model by "old school" Mac users) of each iPod, iPhone and iPad is listed below. Complete technical specifications are merely a click away.

Note that the same Model Identifier may be used for multiple devices and was not used for devices that do not run iOS (formerly called iPhone OS or OS X). Nevertheless, this listing should be useful when trying to track down a particular iPod, iPhone or iPad.

Be mindful of asterisks, as these indicate that particularly important details are provided on the complete specs page.

http://www.everyi.com/by-identifier/ipod-iphone-ipad-specs-by-model-identifier.html