AT&T is apparently testing a new Samsung smartphone with model number SM-6900 that could be the next-generation Samsung Galaxy S5 flagship.

The Samsung Galaxy S5 has already starred in some exciting rumors, with various leaks and reports trying to paint a picture of what to expect from the next-generation flagship Galaxy smartphone.

The latest reports indicated that the Samsung Galaxy S5 will finally sport a metal body instead of the polycarbonate design the company has used so far with its smartphones. Moreover, the Galaxy S5 is also expected to feature fingerprint sensors, eye-scanning technology, and a QHD display with a whopping resolution.

While none of this is confirmed so far, the rumor mill is churning nonetheless in anticipation of the mighty Galaxy S5. According to a new leak, the upcoming flagship may already be in testing for at least one U.S. carrier. The new information comes from trusted tipster @evleaks, who has proved to be accurate on numerous occasions when it came to outing yet-to-be-announced devices or plans in the tech world.

"AT&T is testing a version of that high-res Samsung handset (SM-G900A), giving some support to the theory that it's an int'l flagship (GS5?)," tweeted @evleaks on Wednesday, Dec. 18.

The tipster's mention of a high-resolution display falls in line with the very recent rumor that the Samsung Galaxy S5 would boast a 2K display. The SM-900A model number @evleaks mentioned, however, is intriguing. So far, devices that were thought to be the upcoming Galaxy S5 have surfaced with the model numbers SM-G900F and SM-G900S. The different model numbers could be for models that would work with various carriers.

Considering that the version AT&T is reportedly testing now ends in "A," the tipster's theory that it could be an international version makes sense. As reliable as @evleaks may be, however, it is always advisable to take all leaks, rumors, and speculation with a grain of salt until official confirmation.

Samsung has yet to make an announcement regarding its next-generation Galaxy flagship, but the Galaxy S5 is expected to debut at the Mobile World Congress (MWC) 2014 show in February and go on sale in March or April.