Since 2005, the iPod Shuffle has been the smallest of the iPod family. The telltale signs of identifying this model are its extreme portability, lack of screen, and cheap price. Apple has since come out with 4 different models, and we'll go over them all!
Overview: Even though they come in a variety of colors, they all have the same shape and layout. The picture above is of all the Shuffles starting with the first generation, going left to right, and ending with the fourth generation. If you find that your iPod Shuffle looks strikingly similar to one of these, chances are it is. Below you'll find more on how to accurately discern their looks.
1st Generation: The first iPod Shuffle can be identified by its long shape in which the bottom has a cap that, when removed, exposes the USB dongle for plugging into your computer. Written on the USB part will be the capacity; this is the only Shuffle that has the capacity in a visible place. The rest of the Shuffles will need to be plugged into the computer in order to find out.
2nd Generation: The second gen Shuffle has been reduced considerably, and the button configuration has been moved to the right of the device. The back also sports a handy clip for clipping to your clothes while traveling.
3rd Generation: This is the most dramatically different of all the iPod Shuffles Apple has made. This one completely does away with all buttons with the exception of a slider on the top, accompanied by a headphone jack. The back still has a clip, and it's about as big as an AAA battery. It's very striking to see this Shuffle in person.
4th Generation (current): Seeing that perhaps an incredibly small, button less Shuffle may not be the best idea, they went back to the more classic button circle look. This Shuffle still has the clip on the back, but has regained its once lost 5-way navigation buttons. This looks a lot like the 2nd gen Shuffle, but the button set is in the middle this time, not the side, and has been reduced in size to look more like a square, instead of a rectangle.
There you have it, all of Apples' iPod Shuffles, lined up and identified! In order to find each's capacity, you'll need to plug it into iTunes. If you're looking to sell yours, you are now well equipped to find the most accurate quote for your item!