The second-gen iPhone: 3G, GPS, only slightly thicker

So we've got it on authority that the second-gen iPhone is already well into testing, and numerous units are floating around in super secret pockets. A trusted source got a chance to check one out, here's what we've heard.

• The first thing people will notice: the 2nd gen iPhone will be about the same size and shape as the first gen.
• It will, of course, have 3G. And proper GPS!
• The most noticeable physical difference is back of the phone is no longer metal -- the whole thing is glossy black, from top to bottom. The volume buttons are now chrome.
• Because it's got a little less metal to deal with, it doesn't have quite as many angular edges. The battery is (still) not removable.
• The phone itself will be slightly thicker than the first gen device.
• The headphone jack will no longer be recessed, and will finally be flush with the body.
• The device itself uses roughly the same size and resolution screen as the first generation product.
• No solid word on battery life or storage capacity.

It could ship (or be introduced) as early as July -- but it's worth noting that none of this is necessarily finalized, and any of it could change between now and its introduction. You really never know with Apple!

P.S. -Image via iPod Observer, MacRumors points out it's probably just a case (which we'd likely agree with); we're not by any means claiming the image above is the new iPhone, just an example of what it could look like given the info we received.