Apple retail stores on Thursday began receiving the company's third-generation 4GB iPod shuffle in extremely limited quantities. What follows are a few dozen unboxing and comparison shots, along with some commentary.

Average to mid-size Apple stores we spoke with report receiving only a couple dozen of each color (black and gray) as part of their initial shipment, with more expected by the end of the week. Thus far, the black model is proving to be far more popular with early adopters than the grey model, and was expected to sell out at several locations by day's end.

Apple says the third-gen iPod shuffle ships in packaging that's 40% smaller and 33% lighter than the one used for the second-gen shuffle, and it shows (comparison photos below). The plastic capsule-like container can be concealed almost completely in the palm of your hand.

Inside the box is a pair of Apple Earphones withÂ Remote, a 1.8-inch iPod shuffle Dock sync USB cable, a Quick Start guide, and of course the 4GB shuffle itself. The first thing we noticed is how incredibly tiny the player is. It's no bigger than the length and width of three pieces of Chiclets chewing gum aligned side-by-side. It's also considerably smaller than the mini BiC lighters it resembles.

If you've ever gone diving between the couch cushions to find your misplaced Apple Bluetooth Headset, watch out with the new shuffle. It's most comparable in size — slight shorter but wider, and approximately the same width (not factoring in the headset's earpiece).

On top, there's a 3.5mm stereo headphone jack, a three-way control switch (shuffle, play in order, turn off) and tiny LED that could easily be mistaken for a spec of dust or some other form of debris. Meanwhile, the back sports a new version of the shuffle's familiar clip, only this time with a chromed finish and grainy off-white Apple logo with a bit of sparkle.

More generally speaking, the precision anodized aluminum molding of the player is perfection at its finest. While floating in its retail packaging, the new shuffle appears to lack seams entirely. It's only after a close inspection that you'll notice seams for what looks like a trap door mostly obscured by the clip on the back of the device.

At this juncture, it would also be impossible for Apple to deliver a thinner digital music player without substituting the 3.5mm jack with a new generation of connector. It's that thin.