What is my iOS version is a small online tool which shows the iOS version and display resolution of your iPhone or iPad (or iPod Touch).
But more importantly, it can also distinguish between the iPad 1, 2, 3 and 4 and report on what type of iPad you have. For iPhones, it can distinguish between the iPhone 3GS, 4, 4S and 5.
It also correctly displays the pixel resolution of your screen and Retina display status. These values are misreported by a number of other online screen size checkers.