(Image courtesy of MacRumors)

If there was anyone who still doubts that the fourth-generation iPhone prototype dissected by Gizmodo a few weeks ago is indeed real, another one has now turned up -- this time in Vietnam.

MacRumors is reporting that another fourth-generation iPhone prototype has turned up in Vietnam, and has been thoroughly photographed and even torn down, courtesy of the Taoviet.vn forum. It appears that either someone at Apple has a serious case of butterfingers, since this is now the second such device to land in the hands of someone eager to show it off to the world.

According to the Vietnamese forum at Taoviet.vn, a businessman there purchased this handset in the U.S., together with an iPad. The device appears identical to the same one lost by an Apple engineer back in March and documented last month by Gizmodo, but adds a few new twists.

Unlike the Gizmodo leak, this iPhone clearly indicates on the back that it is a 16GB model -- the previous 4G leak had “XXGB” on the back. This unit also appears to be turned on, as seen in the photo above (and others posted on the MacRumors website), which shows the device at 24 percent battery life remaining. The screen above appears to say “Bonfire!” with some kind of firmware diagnostics displayed.

Additionally, there are no screws at the bottom of this new 4G iPhone, unlike the previous one, which could indicate that this is a production model or a later prototype. Teardown photos of the new iPhone prototype at the MacRumors site also seem to show that the device is running a Apple A4 processor similar to the one used in the iPad.

It’s widely expected that Apple will announce the new handset during WWDC in early June, and possibly start shipping it later the same month in the same manner as last year’s iPhone 3GS model.